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Tetrahydroxyquinone sulfate indicator forex

Benefits of changing from two-stroke to four-stroke engines and other remedial requirements can be evaluated monetized from the standpoint of acute behavioral effects of human exposure to exhaust from these engines. The monetization process depends upon estimates of the magn Lightweight two-stroke cycle aircraft diesel engine technology enablement program, volume 3. Testing confirms the ability of a proposed 4-cylinder version of such an engine to reach the target power at altitude in a highly turbocharged configuration.

The experimental program defines all necessary parameters to permit design of a multicylinder engine for eventual flight applications. Lightweight two-stroke cycle aircraft diesel engine technology enablement program, volume 2. The experimental program defines all necessary parameters to permit a design of a multicylinder engine for eventual flight applications.

Recent Development of the Two-Stroke Engine. II - Design Features. Completing the first paper dealing with charging methods and arrangements, the present paper discusses the design forms of two-stroke engines. Features which largely influence piston running are: a The shape and surface condition of the sliding parts. There is little essential difference between four-stroke and two-stroke engines with ordinary pistons.

In large engines , for example, are always found separately cast or welded frames in which the stresses are taken up by tie rods. Twin piston and timing piston engines often differ from this design. Examples can be found in many engines of German or foreign make. Their methods of operation will be dealt with in the third part of the present paper, which also includes the bibliography.

The development of two-stroke engine design is, of course, mainly concerned with such features as are inherently difficult to master; that is, the piston barrel and the design of the gudgeon pin bearing. Designers of four-stroke engines now-a-days experience approximately the same difficulties, since heat stresses have increased to the point of influencing conditions in the piston barrel.

Features which notably affect this are: a The material. Air at ambient pressure is passed through the compressor where the pressure is increased with the intended purpose of increasing the overall mass flow For a small two-stroke engine that has little excess energy to spare for the operation of a compressor , the Laser-induced breakdown ignition in a gas fed two-stroke engine.

Laser spark benefits as compared to traditional spark plugs are higher compression rate, and possibility of almost any fuel ignition, so lean mixtures burning with lower temperatures could reduce harmful exhausts NO x , CH, etc.

No need in electrode and possibility for multi-point, linear or circular ignition can make combustion even more effective. Laser induced combustion wave appears faster and is more stable in time, than electric one, so can be used for ramjets, chemical thrusters, and gas turbines. To the best of our knowledge, we have performed laser spark ignition of a gas fed two-stroke engine for the first time. Combustion temperature and pressure, exhaust composition, ignition timing were investigated at laser and compared to a regular electric spark ignition in a two-stroke model engine.

Presented results show possibility for improvement of two-stroke engines performance, in terms of rotation rate increase and NO x emission reduction. Such compact engines using locally mined fuel could be highly demanded in remote Arctic areas.

Part 2: Numerical investigations of intake and exhaust flow behaviour. This paper presents the model and simulation result of three-dimensional 3D port flow investigation of a two-stroke poppet valve engine. The objective of the investigation is to conduct a numerical investigation on port flow performance of two-stroke poppet valve engine and compare the results obtained from the experimental investigation. The model is to be used for the future numerical study of the engine.

The volume flow rate results have been compared with the results obtained experimentally as presented in first part of this paper. Two-stroke S. A model engine with disintegrated working cycle was built. Its operation is not autonomous; compression of the working air is performed separately outside the engine by the compressed-air line supply. Pre-compressed charge together with the injected fuel is introduced in the combustion chamber.

The model engine makes possible to determine indicated performance characteristics and its emission capability. Effective measured engine characteristics are of course not comparable with those obtained by a practical engine. The model presented is a two-stroke cycle engine. Exhaust emission picture of the presented engine is comparable with the emission of a modern four-stroke engine.

Figure Crankcase compression drives the scavenging Alex K. The views expressed. Determination of two-stroke engine exhaust noise by the method of characteristics. A computational technique was developed for the method of characteristics solution of a one-dimensional flow in a duct as applied to the wave action in an engine exhaust system. By using the method, it was possible to compute the unsteady flow in both straight pipe and tuned expansion chamber exhaust systems as matched to the flow from the cylinder of a small two-stroke engine.

The radiated exhaust noise was then determined by assuming monopole radiation from the tailpipe outlet. Very good agreement with experiment on an operation engine was achieved in the calculation of both the third octave radiated noise and the associated pressure cycles at several locations in the different exhaust systems. Of particular interest is the significance of nonlinear behavior which results in wave steepening and shock wave formation.

Conversion of a micro, glow-ignition, two-stroke engine from nitromethane-methanol blend fuel to military jet propellant JP The first phase included choosing, developing a test stand for, and baseline testing a nitromethane-methanol-fueled engine. The chosen engine was an A micro engine test stand was developed to load and motor the engine. Instrumentation specific to the low flow rates and high speeds of the micro engine was developed and used to document engine behavior.

The second phase included converting the engine to operate on JP-8, completing JPfueled steady-state testing, and comparing the performance of the JPfueled engine to the nitromethane-methanol-fueled engine. The conversion was accomplished through a novel crankcase heating method; by heating the crankcase for an extended period of time, a flammable fuel-air mixture was generated in the crankcase scavenged engine , which greatly improved starting times.

To aid in starting and steady-state operation, yttrium-zirconia impregnated resin i. This also improved the starting times of the JPfueled engine and ultimately allowed for a second starting time. Finally, the steady-state data from both the nitromethane-methanol and JPfueled micro engine were compared.

The JPfueled engine showed signs of increased engine friction while having higher indicated fuel conversion efficiency and a higher overall system efficiency. The minimal ability of JP-8 to cool the engine via evaporative effects, however, created the necessity of increased cooling air flow. The conclusion reached was that JPfueled micro engines could be viable in application, but not without additional research being conducted on combustion phenomenon and.

Exhaust emissions of low level blend alcohol fuels from two-stroke and four-stroke marine engines. The U. Renewable Fuel Standard mandates that by , 36 billion gallons of renewable fuels must be produced on a yearly basis. Ethanol production is capped at 15 billion gallons, meaning 21 billion gallons must come from different alternative fuel sources.

A viable alternative to reach the remainder of this mandate is iso-butanol. Unlike ethanol, iso-butanol does not phase separate when mixed with water, meaning it can be transported using traditional pipeline methods. Iso-butanol also has a lower oxygen content by mass, meaning it can displace more petroleum while maintaining the same oxygen concentration in the fuel blend.

This research focused on studying the effects of low level alcohol fuels on marine engine emissions to assess the possibility of using iso-butanol as a replacement for ethanol. Three marine engines were used in this study, representing a wide range of what is currently in service in the United States. Two four-stroke engine and one two-stroke engine powered boats were tested in the tributaries of the Chesapeake Bay, near Annapolis, Maryland over the course of two rounds of weeklong testing in May and September.

The engines were tested using a standard test cycle and emissions were sampled using constant volume sampling techniques. Specific emissions for two-stroke and four-stroke engines were compared to the baseline indolene tests.

Because of the nature of the field testing, limited engine parameters were recorded. Therefore, the engine parameters analyzed aside from emissions were the operating relative air-to-fuel ratio and engine speed. Emissions trends from the baseline test to each alcohol fuel for the four-stroke engines were consistent, when analyzing a single round of testing.

The same trends were not consistent when comparing separate rounds because of uncontrolled weather conditions and because the four-stroke engines operate without fuel control feedback during full load conditions. Emissions trends from the baseline test to each. Gasoline-related organics in Lake Tahoe before and after prohibition of carbureted two-stroke engines. On June 1, , carbureted two-stroke engines were banned on waters within the Lake Tahoe Basin of California and Nevada.

The main gasoline components MTBE methyl tert-butyl ether and BTEX benzene, toluene, ethylbenzene, and xylenes were present at detectable concentrations in all samples taken from Lake Tahoe during prior to the ban. Samples taken from through after the ban contained between 10 and 60 percent of the pre-ban concentrations of these compounds, with MTBE exhibiting the most dramatic change a 90 percent decrease.

Polycyclic aromatic hydrocarbon PAH compounds are produced by high-temperature pyrolytic reactions. They were sampled using semipermeable membrane sampling devices in Lake Tahoe and nearby Donner Lake, where carbureted two-stroke engines are legal. The number of PAH compounds and their concentrations are related to boat use.

Other sources of PAH, such as atmospheric deposition, wood smoke, tributary streams, and automobile exhaust do not contribute large amounts of PAH to Lake Tahoe. Similar numbers of PAH compounds and concentrations were found in Lake Tahoe before and after the ban of carbureted two-stroke engines. Small Engine Repair.

Two-Stroke and Four-Stroke Cycle. This curriculum guide is intended to assist persons teaching a course in repairing two- and four-stroke cycle small engines. Addressed in the individual units of instruction are the following topics: safety, tools, fasteners, and measurement techniques; basic small engine theory engine identification and inspection, basic engine principles and…. Coast Guard pollution abatement program - Two-stroke cycle outboard engine emissions.

This report documents the results of emissions tests performed on three old and two new outboard engines. Tests of the emissions were made before and after water contact. Older engines were tested in as-received condition, tuned to factory specificat A numerical analysis is presented on the effects of the engine speed, injection angle, droplet distribution function, and spray cone angle on the flow field, spray penetration and vaporization, and turbulence in a turbocharged motored two-stroke diesel engine.

The results indicate that the spray penetration and vaporization, velocity, and turbulence kinetic energy increase with the intake swirl angle. Good spray penetration, vaporization, and mixing can be achieved by injecting droplets of diameters between 50 and microns along a deg cone at about deg before top-dead-center for an intake swirl angle of 30 deg. The spray penetration and vaporization were found to be insensitive to the turbulence levels within the cylinder. The results have also indicated that squish is necessary in order to increase the fuel vaporization rate and mixing.

An OCP direct fuel injected, 1. The engine currently demonstrates low brake specific fuel consumption capability and an excellent power to weight ratio. Increasing the volumetric efficiency of Diesel engines by intake pipes. Development of a method for calculating the volumetric efficiency of piston engines with intake pipes.

Application of this method to the scavenging pumps of two-stroke -cycle engines with crankcase scavenging and to four-stroke-cycle engines. The utility of the method is demonstrated by volumetric-efficiency tests of the two-stroke -cycle engines with crankcase scavenging. Its practical application to the calculation of intake pipes is illustrated by example. SAE Int. Engines , vol. Caton, S. Williams, R. Kamin, D.

Luning -Prak, L. Hamilton and J. Detroit, MI, Feb. Cowart, M. Carr, P. Caton, L. Stoulig, D. Luning -Prak, A. Moore and L. Direct comparison was made to operation on E0 ethanol-free gasoline to determine the effects of increased ethanol on engine durability. Testing was conducted using a hour wide-open throttle WOT test protocol, a typical durability cycle used by the outboard marine industry. Use of E15 resulted in reduced CO emissions, as expected for open-loop, non-feedback control engines.

HC emissions effects were variable. Exhaust gas and engine operating temperatures increased as a consequence of leaner operation. The 9. The HP, four-stroke, supercharged Verado engine and the HP, two-stroke legacy engine tested with E15 fuel failed to complete the durability test. The Verado engine failed three exhaust valves at endurance hours while the HP legacy engine failed a main crank bearing at endurance hours.

All E0-dedicated engines completed the durability cycle without incident. Additional testing is necessary to link the observed engine failures to ethanol in the test fuel. The first of a series of high efficiency, high bmep, turbocharged two-stroke cycle diesel engines ; the general motors EMD FB engine.

The FB engine combines the highest thermal efficiency with the highest specific output of any EMD engine to date. The FB Series incorporates compression ratio with a fire ring piston and an improved turbocharger design. Engine components included in the FB engine provide very high output levels with exceptional reliability.

This paper also describes the performance of the lower rated Model EC engine series which feature high thermal efficiency and utilize many engine components well proven in service and basic to the Model FB Series. A method of producing lithium of high purity from lithium aluminum alloys using an engineered scavenger compound, comprising: I preparing an engineered scavenger compound by: a mixing and heating compounds of TiO2 and Li2CO3 at a temperature sufficient to dry the compounds and convert Li.

The object of the investigation presented in this report was to determine the effects of increasing the air charge and scavenging the clearance volume of a 4-stroke-cycle compression-ignition engine having a vertical-disk form combustion chamber. Boosting the inlet-air pressure with normal valve timing increased the indicated engine power in proportion to the additional air inducted and resulted in smoother engine operation with less combustion shock.

The improved combustion characteristics result in lower specific fuel consumption, and a clearer exhaust. On PMWs and two-stroke engines. PubMed Central. He was approximately m offshore. The man motioned to his sister, who was riding another PMW, to follow him across the lake. She did so, but as the turned her head to check for other boat traffic, her brother suddenly slowed down and her machine rode right up on his back, crushing him against his handlebars.

His sister, a nurse, held her brother's head above water until help arrived but, 48 minutes after the moment of impact, he was pronounced dead at the Shuswap Lake General Hospital. He had suffered a ruptured aorta.

This investigation was conducted to determine the effect of more complete scavenging on the full throttle power and the fuel consumption of a four-stroke-cycle engine. The NACA single-cylinder universal test engine equipped with both a fuel-injection system and a carburetor was used. The engine was scavenged by using a large valve overlap and maintaining a pressure in the inlet manifold of 2 inches of mercury above atmospheric.

The maximum valve overlap used was degrees. Tests were conducted for a range of compression ratios from 5. Except for variable speed tests, all tests were conducted at an engine speed of 1, r. The results of the tests show that the clearance volume of an engine can be scavenged by using a large valve overlap and about 2 to 5 inches of mercury pressure difference between the inlet and exhaust valve.

With a fuel-injection system when the clearance volume was scavenged , a b. An increase of approximately 10 pounds per square inch b. Two-stroke diesels meet Macau electric power needs. In February , the second and last section of the third low-speed diesel extension to the Coloane Power Station was handed over to Companhia de Electricidade de Macau CEM by an international consortium.

The flex fuel engine produces stock engine power on any blend of etha Rotary vane type IC engine with built-in scavenging air blower. This patent describes a rotary internal combustion engine. This engine consists of: a housing assembly including three sections and having a single common power shaft, the three sections being integrally connected together and operatively connected together into a unitary self-contained engine , air and fuel mixture intake conduit means communicatively connected to a first of the three sections, means in the first section to perform admission and compression of the air and fuel mixture admitted from the conduit means, means to convey the compressed air and fuel mixture to a second of the three sections.

In the second section the compressed air is ignited with a fuel mixture and to permit expansion of the ignited air and fuel mixture to thereby furnish power strokes to the power shaft. In the second section for exhausting the gaseous products of combustion, air blower in the third of the three sections driven by the power shaft. Hydrogen scavengers. There has been invented a codeposition process for fabricating hydrogen scavengers.

First, a. Numerical simulation of the flow field and fuel sprays in an IC engine. A two-dimensional model for axisymmetric piston-cylinder configurations is developed to study the flow field in two-stroke direct-injection Diesel engines under motored conditions. The model accounts for turbulence by a two-equation model for the turbulence kinetic energy and its rate of dissipation.

A discrete droplet model is used to simulate the fuel spray, and the effects of the gas phase turbulence on the droplets is considered. It is shown that a fluctuating velocity can be added to the mean droplet velocity every time step if the step is small enough. Good agreement with experimental data is found for a range of ambient pressures in Diesel engine -type microenvironments. The effects of the intake swirl angle in the spray penetration, vaporization, and mixing in a uniflow- scavenged two-stroke Diesel engine are analyzed.

It is found that the swirl increases the gas phase turbulence levels and the rates of vaporization. A process for removing fission products from reactor liquid fuel without interfering with the reactor's normal operation or causing a significant change in its fuel composition is described. The process consists of mixing a liquid scavenger alloy composed of about 44 at.

Industrial Education. Part of a series of curriculum guides dealing with industrial education in junior high schools, this guide provides the student with information and manipulative experiences on small gasoline engines. Included are sections on shop adjustment, safety, small engines , internal combustion, engine construction, four stroke engines , two stroke engines ,….

A Geospatial Scavenger Hunt. Martinez, Adriana E. With the use of technology such as Global Positioning System GPS units and Google Earth for a simple-machine scavenger hunt, you will transform a standard identification activity into an exciting learning experience that motivates students, incorporates practical skills in technology, and enhances students' spatial-thinking skills. In the…. This report describes the experimental evaluation of a prototype free piston engine - linear alternator FPLA system developed at Sandia National Laboratories.

The opposed piston design wa developed to investigate its potential for use in hybrid electric vehicles HEVs. The system is mechanically simple with two - stroke uniflow scavenging for gas exchange and timed port fuel injection for fuel delivery, i. Electrical power is extracted from piston motion through linear alternators wh ich also provide a means for passive piston synchronization through electromagnetic coupling. The engine - alternator system was designed, assembled and operated over a 2 - year period at Sandia National Laboratories in Livermore, CA.

This report primarily contains a description of the as - built system, modifications to the system to enable better performance, and experimental results from start - up, motoring, and hydrogen combus tion tests. Enhanced electrohydrodynamic force generation in a two-stroke cycle dielectric-barrier-discharge plasma actuator. An approach for electrohydrodynamic EHD force production is proposed with a focus on a charge cycle on a dielectric surface.

The cycle, consisting of positive-charging and neutralizing strokes, is completely different from the conventional methodology, which involves a negative-charging stroke, in that the dielectric surface charge is constantly positive. The two-stroke charge cycle is realized by applying a DC voltage combined with repetitive pulses.

Simulation results indicate that the negative pulse eliminates the surface charge accumulated during constant voltage phase, resulting in repetitive EHD force generation. The time-averaged EHD force increases almost linearly with increasing repetitive pulse frequency and becomes one order of magnitude larger than that driven by the sinusoidal voltage, which has the same peak-to-peak voltage. Atmospheric scavenging exhaust.

Solid propellant rocket exhaust was directly utilized to ascertain raindrop scavenging rates for hydrogen chloride. The airborne HCl concentration varied from 0. Two chambers were used to conduct the experiments. A large, rigid walled, spherical chamber stored the exhaust constituents while the smaller chamber housing all the experiments was charged as required with rocket exhaust HCl.

Surface uptake experiments demonstrated an HCl concentration dependence for distilled water. Sea water and brackish water HCl uptake was below the detection limit of the chlorine-ion analysis technique employed. Plant life HCl uptake experiments were limited to corn and soybeans. Plant age effectively correlated the HCl uptake data. Metallic corrosion was not significant for single 20 minute exposures to the exhaust HCl under varying relative humidity.

University of Idaho's low-speed flex fuel direct-injected cc two-stroke rear drive snowmobile. The University of Idahos entry into the SAE Clean Snowmobile Challenge uses a Ski-Doo XP chassis with a low-speed cc direct-injection two-stroke powered snowmobile modified for flex fuel use on blended ethanol fuel.

A battery-less direct While natural hepatitis C virus HCV infection results in highly diverse quasispecies of related viruses over time, mutations accumulate more slowly in tissue culture, in part because of the inefficiency of replication in cells.

To create a highly diverse population of HCV particles in cell culture and identify novel growth-enhancing mutations, we engineered a library of infectious HCV with all codons represented at most positions in the ectodomain of the E2 gene. We evaluated these mutants for changes in particle-to-infectious-unit ratio, sensitivity to neutralizing antibody or CD81 large extracellular loop CDLEL inhibition, entry factor usage, and buoyant density profiles. This shift from SR-BI usage did not correlate with a change in the buoyant density profiles of the variants, suggesting an altered E2-SR-BI interaction rather than changes in the virus-associated lipoprotein-E2 interaction.

Our results demonstrate that residues influencing SR-BI usage are distributed across E2 and support the development of large-scale mutagenesis studies to identify viral variants with unique functional properties. Characterizing variant viruses can reveal new information about the life cycle of HCV and the roles played by different viral genes.

However, it is difficult to recapitulate high levels of diversity in the laboratory because of limitations in the HCV culture system. To overcome this limitation, we engineered a library of mutations into the E2 gene in the context of an infectious clone of the virus.

We used this library of viruses. Negotiating role management through everyday activities: narratives in action of two stroke survivors and their spouses. To manage social roles is a challenging part of self-management post-stroke. This study explored how stroke survivors act as role managers with their spouses in the context of everyday activities.

Two stroke survivors with a first time stroke living at home with a spouse were included. Data were generated through participant observations at their own environment at 3, 6, 9, 15 and 21 months post-discharge.

The narrative analysis focused on the actions of participants. Daily activities can be understood as an arena where role management and a meaningful live is negotiated and co-constructed with others. Everyday activities gave stroke survivors and their spouses insight into stroke survivors' capacities in daily situations.

This was sometimes empowering, and other times conflicting when a spouse had negative perceptions of the abilities of the stroke survivors. The findings add to the current understanding of self-management and role management with regard to how these are situated in everyday activities. Daily activities can help both spouses to reflect and understand about self-management, role management and comanagement in daily life.

Moreover, observing stroke survivors in everyday situations provides professionals with concrete pictures of stroke survivors' performance and self-management in interaction with their spouses. Implications for Rehabilitation Self-management is a dynamic process in which individuals actively manage a chronic condition and finally live a meaningful life with a long-term chronic condition; self-management can be divided into medical, role, and emotional management; comanagement is when individuals activate resources and use the capacities of other persons to manage a situation together.

Self-management is situated in everyday activities. Everyday activities give stroke. A scavenging mask is a device positioned over a patient's nose to deliver anesthetic or analgesic gases to the High Throughput Immunomagnetic Scavenging Technique for Journal Article This article describes a novel immunomagnetic scavenging IMSc technique for extracting cholinesterase inhibitors from aqueous matrixes using biological targeting and antibody-based extraction.

Free-piston engine. In particular, a free-piston, two-stroke autoignition internal combustion engine including an electrical generator having a linear alternator with a double-ended free piston that oscillates inside a closed cylinder is provided. Fuel and air are introduced in a two-stroke cycle fashion on each end, where the cylinder charge is compressed to the point of autoignition without spark plugs.

The piston is driven in an oscillating motion as combustion occurs successively on each end. The engine is characterized by high thermal efficiency and low NO. The engine is particularly suited for generating electrical current in a hybrid automobile. Scavenging is a well documented feeding behavior among many arthrop predators.

However, quantifying scavenging feeding activity is not well understood because many predators are small elusive. This makes directly observing predation events in nature almost impossible. If predators prefer dead prey Americans with Disabilities Act Scavenger Hunt. This article describes a scavenger hunt for Business Law students.

The modulated and battery-less direct-injection system used to decrease Melatonin and its precursors scavenge nitric oxide. Nitric oxide NO scavenging activity of melatonin, N-acetylhydroxytryptamine, serotonin, 5-hydroxytryptophan and L-tryptophan was examined by the Griess reaction using flow injection analysis.

The Griess reagent stoichiometrically reacts with NO2-, which was converted by a cadmium-copper reduction column from the stable end products of NO oxidation. Except for tryptophan, all the compounds examined scavenged NO in a dose-dependent manner. Melatonin, which has a methoxy group in the 5-position and an acetyl side chain, exhibited the most potent scavenging activity among the compounds tested.

Serotonin, N-acetylhydroxytryptamine, and 5-hydroxytryptophan, respectively, showed moderate scavenging activity compared to melatonin. Anaesthesia machine: checklist, hazards, scavenging. From a simple pneumatic device of the early 20 th century, the anaesthesia machine has evolved to incorporate various mechanical, electrical and electronic components to be more appropriately called anaesthesia workstation.

Modern machines have overcome many drawbacks associated with the older machines. However, addition of several mechanical, electronic and electric components has contributed to recurrence of some of the older problems such as leak or obstruction attributable to newer gadgets and development of newer problems.

No single checklist can satisfactorily test the integrity and safety of all existing anaesthesia machines due to their complex nature as well as variations in design among manufacturers. Human factors have contributed to greater complications than machine faults. Therefore, better understanding of the basics of anaesthesia machine and checking each component of the machine for proper functioning prior to use is essential to minimise these hazards. Clear documentation of regular and appropriate servicing of the anaesthesia machine, its components and their satisfactory functioning following servicing and repair is also equally important.

Trace anaesthetic gases polluting the theatre atmosphere can have several adverse effects on the health of theatre personnel. Therefore, safe disposal of these gases away from the workplace with efficiently functioning scavenging system is necessary. Other ways of minimising atmospheric pollution such as gas delivery equipment with negligible leaks, low flow anaesthesia, minimal leak around the airway equipment facemask, tracheal tube, laryngeal mask airway, etc.

Anaesthesia Machine: Checklist, Hazards, Scavenging. From a simple pneumatic device of the early 20th century, the anaesthesia machine has evolved to incorporate various mechanical, electrical and electronic components to be more appropriately called anaesthesia workstation. Haemoglobin scavenging after subarachnoid haemorrhage. Rapid and effective clearance of cell-free haemoglobin after subarachnoid haemorrhage SAH is important to prevent vasospasm and neurotoxicity and improve long-term outcome.

Haemoglobin is avidly bound by haptoglobin, and the complex is cleared by CD expressed on the membrane surface of macrophages. We studied the kinetics of haemoglobin and haptoglobin in cerebrospinal fluid after SAH. We show that haemoglobin levels rise gradually after SAH.

Haptoglobin levels rise acutely with aneurysmal rupture as a result of injection of blood into the subarachnoid space. Although levels decline as haemoglobin scavenging occurs, complete depletion of haptoglobin does not occur and levels start rising again, indicating saturation of CD sites available for haptoglobin-haemoglobin clearance. In a preliminary neuropathological study we demonstrate that meningeal CD expression is upregulated after SAH, in keeping with a proinflammatory state.

However, loss of CD occurs in meningeal areas with overlying blood compared with areas without overlying blood. Microscope Image of Scavenged Particles. This image from NASA's Phoenix Mars Lander's Optical Microscope shows a strongly magnetic surface which has scavenged particles from within the microscope enclosure before a sample delivery from the lander's Robotic Arm. The particles correspond to the larger grains seen in fine orange material that makes up most of the soil at the Phoenix site.

They vary in color, but are of similar size, about one-tenth of a millimeter. As the microscope's sample wheel moved during operation, these particles also shifted, clearing a thin layer of the finer orange particles that have also been collected. Together with the previous image, this shows that the larger grains are much more magnetic than the fine orange particles with a much larger volume of the grains being collected by the magnet.

The image is 2 milimeters across. It is speculated that the orange material particles are a weathering product from the larger grains, with the weathering process both causing a color change and a loss of magnetism. Peroxynitrite scavenging activity of herb extracts. Peroxynitrite ONOO - is a cytotoxicant with strong oxidizing properties toward various cellular constituents, including sulphydryls, lipids, amino acids and nucleotides and can cause cell death, lipid peroxidation, carcinogenesis and aging.

The aim of this study was to characterize ONOO - scavenging constituents from herbs. Twenty-eight herbs were screened for their ONOO - scavenging activities with the use of a fluorometric method. The extracts exhibited dose-dependent ONOO - scavenging activities. We found that witch hazel Hamamelis virginiana L.

Hamamelitannin, the major active component of witch hazel bark, was shown to have a strong ability to scavenge ONOO -. It is suggested that hamamelitannin might be developed as an effective peroxynitrite scavenger for the prevention of ONOO - involved diseases. Dielectric polymer: scavenging energy from human motion. More and more sensors are embedded in human body for medical applications, for sport. The short lifetime of the batteries, available on the market, reveals a real problem of autonomy of these systems.

A promising alternative is to scavenge the ambient energy such as the mechanical one. Up to now, few scavenging structures have operating frequencies compatible with ambient one. And, most of the developed structures are rigid and use vibration as mechanical source.

For these reasons, we developed a scavenger that operates in a large frequency spectrum from quasi-static to dynamic range. This generator is fully flexible, light and does not hamper the human motion. Thus, we report in this paper an analytical model for dielectric generator with news electrical and mechanical characterization, and the development of an innovating application: scavenging energy from human motion.

The generator is located on the knee and design to scavenge 0. The evaluation of potential limonene scavengers. This work is the study of different scavengers of limonene. Limonene is a citrus-based, low toxicity, hydrocarbon solvent for cleaning circuit boards and other parts. Though almost all limonene evaporates after cleaning procedures, trace residual limonene would be a concern if allowed to migrate freely through a sealed system.

This work was charted to investigate materials that would effectively scavenge and permanently immobilize trace limonene. A number of adsorbents were evaluated. Additionally, a scheme for scavenging limonene by chemical reaction was investigated at Sandia.

This attempt was not successful. The details of this investigation are found at the end of this report. Effect of concentration and molecular weight of chitosan and its derivative on the free radical scavenging ability. Chitosan is a biodegradable and biocompatible natural scaffold material, which has numerous applications in biomedical sciences.

The scavenging mechanism was also discussed. The results indicated that the free radical scavenging ability of chitosan scaffold material significantly depends on the chitosan concentration and shows interesting kinetic change. Within the experimental concentration range, the optimal concentration of chitosan was 0. The molecular weight of chitosan also attributed to the free radical scavenging ability.

Comparison between chitosan and its derivative found that carboxymethyl chitosan possessed higher scavenging ability. Killer whales and whaling: the scavenging hypothesis. Killer whales Orcinus orca frequently scavenged from the carcasses produced by whalers.

This practice became especially prominent with large-scale mechanical whaling in the twentieth century, which provided temporally and spatially clustered floating carcasses associated with loud acoustic signals. The carcasses were often of species of large whale preferred by killer whales but that normally sink beyond their diving range.

In the middle years of the twentieth century floating whaled carcasses were much more abundant than those resulting from natural mortality of whales, and we propose that scavenging killer whales multiplied through diet shifts and reproduction. During the s the numbers of available carcasses fell dramatically with the cessation of most whaling in contrast to a reasonably stable abundance of living whales , and the scavenging killer whales needed an alternative source of nutrition.

Diet shifts may have triggered declines in other prey species, potentially affecting ecosystems, as well as increasing direct predation on living whales. Free Radical Scavenging Properties of Annona squamosa. Annona squamosa has extensively been used in the traditional and folkloric medicine and found to possess many biological activities.

The present investigations dealt with the free radical scavenging activity of four extracts using various techniques such as total reducing power estimation, total phenolic count, 1,1-diphenylpicryl hydrazyl DPPH radical scavenging effect, evaluation of ABTS cation decolorisation capacity, FRAP assay, hdroxyl radical scavenging assay, super oxide assay and Nitric oxide radical scavenging assay of the extracts. The results showed that the four extracts of Annona squamosa showed significant reducing power in four extracts.

The total phenolic contents in petroleum ether, chloroform, ethyl acetate, methanol extracts and positive control were 0. The percentage of hydroxyl radical scavenging increased with the increasing concentration of the extracts. The results revealed strong antioxidants in four extracts may lead to the development of potent.

Nature or Nurture? Gender Roles Scavenger Hunt. The examination of gender roles and stereotypes and their subsequent impact on sexual behavior is a concept for discussion in many sex education courses in college and sex education units in high school.

This analysis often leads to a discussion of the impact of nature vs. The gender roles scavenger hunt is an interactive…. Rare earth element scavenging in seawater. Examinations of rare earth element REE adsorption in seawater, using a variety of surface-types, indicated that, for most surfaces, light rare earth elements LREEs are preferentially adsorbed compared to the heavy rare earths HREEs.

Exceptions to this behavior were observed only for silica phases glass surfaces, acid-cleaned diatomaceous earth, and synthetic SiO 2. The affinity of the rare earths for surfaces can be strongly affected by thin organic coatings. Glass surfaces which acquired an organic coating through immersion in Tampa Bay exhibited adsorptive behavior typical of organic-rich, rather than glass, surfaces.

Models of rare earth distributions between seawater and carboxylate-rich surfaces indicate that scavenging processes which involve such surfaces should exhibit a strong dependence on pH and carbonate complexation. Scavenging models involving carboxylate surfaces produce relative REE abundance patterns in good general agreement with observed shale-normalized REE abundances in seawater. Scavenging by carboxylate-rich surfaces should produce HREE enrichments in seawater relative to the LREEs and may produce enrichments of lanthanum relative to its immediate trivalent neighbors.

Due to the origin of distribution coefficients as a difference between REE solution complexation which increases strongly with atomic number and surface complexation which apparently also increases with atomic number the relative solution abundance patterns of the REEs produced by scavenging reactions can be quite complex. Brain neuroprotection by scavenging blood glutamate. Excess glutamate in brain fluids characterizes acute brain insults such as traumatic brain injury and stroke.

Its removal could prevent the glutamate excitotoxicity that causes long-lasting neurological deficits. As blood glutamate scavenging has been demonstrated to increase the efflux of excess glutamate from brain into blood, we tested the prediction that oxaloacetate-mediated blood glutamate scavenging causes neuroprotection in a pathological situation such as closed head injury CHI , in which there is a well established deleterious increase of glutamate in brain fluids.

The treatment with 0. Scavenging and recombination kinetics in a radiation spur: The successive ordered scavenging events. This study describes stochastic models to investigate the successive ordered scavenging events in a spur of four radicals, a model system based on a radiation spur.

Three simulation models have been developed to obtain the probabilities of the ordered scavenging events: i a Monte Carlo random flight RF model, ii hybrid simulations in which the reaction rate coefficient is used to generate scavenging times for the radicals and iii the independent reaction times IRT method.

The results of these simulations are found to be in agreement with one another. In addition, a detailed master equation treatment is also presented, and used to extract simulated rate coefficients of the ordered scavenging reactions from the RF simulations. These rate coefficients are transient, the rate coefficients obtained for subsequent reactions are effectively equal, and in reasonable agreement with the simple correction for competition effects that has recently been proposed.

Although raccoons are known as one of the most common scavengers in the U. In this research, the seasonal pattern of raccoon scavenging and its effect on human decomposition was investigated using human cadavers placed at the Anthropological Research Facility ARF of the University of Tennessee, Knoxville UTK between February and December The results reveal that i the frequency of scavenging increases during summer, ii scavenging occurs relatively immediately and lasts shorter in summer months, and iii scavenging influences the decomposition process by hollowing limbs and by disturbing insect activities, both of which eventually increases the chance of mummification on the affected body.

This information is expected to help forensic investigators identify raccoon scavenging as well as make a more precise interpretation of the effect of raccoon scavenging on bodies at crime scenes. A gas- scavenging apparatus is a device intended to collect excess anesthetic, analgesic, or trace Scavenger Receptors and Resistance to Inhaled Allergens.

We plan to continue two especially interesting aspects of these studies. First, the epigenetic control Granucci, F. Petralia, M. Urbano , S. Citterio, F. Di Tota, L Energy scavenging sources for biomedical sensors. Energy scavenging has increasingly become an interesting option for powering electronic devices because of the almost infinite lifetime and the non-dependence on fuels for energy generation. Moreover, the rise of wireless technologies promises new applications in medical monitoring systems, but these still face limitations due to battery lifetime and size.

A trade-off of these two factors has typically governed the size, useful life and capabilities of an autonomous system. Energy generation from sources such as motion, light and temperature gradients has been established as commercially viable alternatives to batteries for human-powered flashlights, solar calculators, radio receivers and thermal-powered wristwatches, among others. Research on energy harvesting from human activities has also addressed the feasibility of powering wearable or implantable systems.

Biomedical sensors can take advantage of human-based activities as the energy source for energy scavengers. This review describes the state of the art of energy scavenging technologies for powering sensors and instrumentation of physiological variables. After a short description of the human power and the energy generation limits, the different transduction mechanisms, recent developments and challenges faced are reviewed and discussed.

Atmospheric Hydrogen Scavenging : from Enzymes to Ecosystems. We have known for 40 years that soils can consume the trace amounts of molecular hydrogen H2 found in the Earth's atmosphere. This process is predicted to be the most significant term in the global hydrogen cycle.

However, the organisms and enzymes responsible for this process were only recently identified. Pure culture experiments demonstrated that several species of Actinobacteria, including streptomycetes and mycobacteria, can couple the oxidation of atmospheric H2 to the reduction of ambient O2. A combination of genetic, biochemical, and phenotypic studies suggest that these organisms primarily use this fuel source to sustain electron input into the respiratory chain during energy starvation.

This process is mediated by a specialized enzyme, the group 5 [NiFe]-hydrogenase, which is unusual for its high affinity, oxygen insensitivity, and thermostability. Atmospheric hydrogen scavenging is a particularly dependable mode of energy generation, given both the ubiquity of the substrate and the stress tolerance of its catalyst.

This minireview summarizes the recent progress in understanding how and why certain organisms scavenge atmospheric H2. At the end, a detailed description of the method actually used is handed in for permanent record, together with any comments or suggestions, and the results of the analysis reported in the proper manner. As for estimating the accuracy of his work, it can be said that the determinator is usually an optimist in thought and expression, while the analyst is a confirmed pessimist.

The determinator reports silica in glass as The analyst, who knows that he is doing nicely to insure results in the first decimal place, reports The prime importance of a notebook is to preserve the record. Naturally, then, the principal concern is that the record be legible and intelligible at some later date when the record is cold and all memory of the event has been long lost. Preferably the notebook should be a bound book with fixed pages and of sufficient value that it will not be lightly discarded.

The record should be kept in ink as this is most durable. The relevant data should all be entered, including the date, the source, character, and number or other designation of the sample, all weights and readings taken during the analysis, a brief mention of the method of analysis used, any numerical factors introduced, the results with any explanatory comment, and finally the signature of the analyst.

The arrangement is entirely an individual matter, but should be intelligible to another without undue effort in the deciphering of shorthand symbols or sloppy penmanship. Among the emphatic doit'fs of record keeping. Equally bad is a numerical entry without explanation. The problem of significant figures, methods of computation, the rejection of data, and related topics were discussed in Willard and Furman, 3rd Ed. A more extensive treatment of these subjects will be found in other places.

The rejection of data should be justified by some definite reason or observed fault in the process leading to the data. Data otherwise apparently satisfactory but in disagreement with other data on the same measurement should be rejected only on a probability basis when it can be shown that the departure from the mean is far greater than the average deviation, and this can not be done with less than four values.

The selection of data is a matter of experience, critical evaluation, and honesty. The mathematical rules governing significant figures are more definite, and precision should not be confused with accuracy. But even in this, in chemical work, much is left to personal judgement and to good taste. Free chlorine and bromine attack it easily, boiling, concentrated sulfuric acid slowly, and the following materials attack it so readily that they should never be heated in platinum vessels: The hydroxides, nitrates, and cyanides of the alkali metals and.

At high temperatures, platinum allows the gases of the flame to diffuse through it quite readily and this may cause the reduction of some substances not otherwise easily reduced. If the crucible is open, diffusion into the air is so rapid that this effect is much less noticeable, but in a covered crucible heated by a gas flame there is a strong reducing atmosphere in the crucible.

Ferric oxide heated in this way is partly reduced to the metal; even in the presence of fused sodium carbonate some reduction seems to occur. The iron then alloys with the platinum, and no matter how thoroughly the latter is cleaned, it will tarnish on ignition, due to the formation of a film of ferric oxide.

If this is removed and the crucible again heated, the same thing occurs. This contamination is so common that it is difficult to find a crucible entirely free from iron. It is advisable, therefore, to use a porcelain crucible for the ignition of iron compounds, or if platinum is used, to be sure that the crucible is placed in a slanting position with free access to air.

Another illustration of this permeability of platinum is the reduction of sodium sulfate. This salt may be fused in an open crucible without change, but in a covered crucible it is partly reduced to sodium sulfide, as shown by treating it with dilute acid. A platinum crucible should never be heated so that the inner cone of the flame touches it. This causes the formation of a carbide of platinum and makes the crucible very brittle. Whenever possible, the Meker burner should be used, since there is then no inner cone and the flame is uniform.

When the surface of platinum becomes gray or crystalline, it should be polished with sea sand or powdered pumice. If sand does not readily remove all stains, fusion with potassium or sodium bisulfate or sometimes borax, boiling with hydrochloric acid or with nitric acid but never with a mixture of the two will usually be. If this is not satisfactory, heating with a mixture of equal parts of concentrated hydrofluoric acid and hydrochloric acid or fusion with potassium acid fluoride will sometimes assist.

Iron stains are readily removed by heating the covered crucible with a gram of ammonium chloride at the full heat of a burner. Crucibles must always be kept polished, and must not be bent or injured in any way. If they become deformed, they should be reshaped on a form of the same style.

Never try to rub out a dent. Take it to the instructor. New platinum crucibles are often covered with a film of iron, which should be removed by boiling in hydrochloric acid for an hour or two before the crucible is heated. Otherwise the iron alloys with the platinum and can not afterwards be completely removed. Hot, concentrated perchloric acid is a powerful oxidizing agent and a powerful dehydrating agent; cold and dilute, it has neither oxidizing nor dehydrating properties and has only the characteristics of a strong acid.

This solvent power is often enhanced by mixing it with phosphoric acid or sulfuric acid. It follows then, that perchloric acid is dangerous only when hot and concentrated and in the presence of some easily oxidizable material such as organic matter. Perchloric acid can be used to destroy organic matter, but nitric acid must always be added first while the perchloric acid is still dilute.

Notable exceptions to this rule are coal and coke; here a contact catalyst such as chromic acid is used to speed the oxidation. The nitric acid oxidizes the easily oxidizable material which would act violently with concentrated perchloric acid, and the remaining more difficultly oxidizable material is then finally destroyed by the concentrated perchloric acid.

Such procedures are widely used in the analysis of rubber, leather, coal, and similar materials for their inorganic constituents. A progression of colors, in the oxidation of organic material, changing from a light yellow, to a straw, to light brown, to dark brown, generally precedes a perchlorate explosion. If such a color change 4 A thorough discussion of the preparation, properties, and uses of perchloric acid will be found in the following booklets by G.

Frederick Smith, published by The G. Concentrated perchloric acid is marketed as 60 or 72 per cent acid and is a perfectly stable chemical which can be kept for any length of time. Anhydrous perchloric acid or acid of greater concentration than 85 per cent explodes ultimately on standing and should never be made in appreciable quantities or stored for any period of time. A monohydrate of perchloric acid, corresponding to Commercial concentrated perchloric acid, on boiling at normal pressure, concentrates to a constant boiling mixture of Boiling perchloric acid solutions of this concentration or lower concentrations is a perfectly safe operation.

Care should be exercised in places where quantities of perchloric acid are being boiled that the perchloric acid vapors are not allowed to accumulate as condensate, particularly on wood or dusty hoods or flues. Such hoods are best made of tile or transite and should be flushed out occasionally. The filtration of a solution containing dilute perchloric acid on filter paper is perfectly permissible, but washing should be exceptionally thorough to remove all perchloric acid if the filter is to be ignited.

Otherwise a violent deflagration or even an explosion may occur during the drying. An additional final washing with dilute ammonia, if permissible, eliminates this tendency. Certain salts of perchloric acid, principally those of magnesium and barium, are excellent drying agents, the former rivalling phosphorus pentoxide in effectiveness.

These are very stable compounds and highly satisfactory for practically all drying problems. They should not be used in the presence of a strong acid and organic matter, such as cotton, rubber stoppers, or organic liquids. Several serious explosions have resulted from drying with magnesium perchlorate organic liquids which had previously been in contact with sulfuric acid and had been poorly washed.

The perchlorates of all of the heavy metals are soluble in water, and surprisingly, some metal perchlorates are soluble in organic solvents. Advantage of this is taken in the separation of sodium and potassium. Solutions of perchlorates in organic solvents in the presence of acids are dangerous, however, and should never be heated or.

An alcoholic solution of perchloric acid should never be heated unless considerable water is present and on no account should be evaporated. When properly used, perchloric acid and its salts are without hazard, and hundreds of applications of them are being so continuously developed as to make perchloric acid almost as indispensable as nitric, sulfuric, and hydrochloric acids. In many cases perchloric acid has effected great savings in time and expense; it has simplified and improved the accuracy of many analytical procedures; and in many cases its application can be made to accomplish things which can be done by no other method.

However, before using perchloric acid or its salts in a new application, consider the facts of the foregoing discussion. This procedure not only involves a considerable expenditure of time but also a loss of accuracy, since an error in one separation affects the others. The trend of modern analytical chemistry is toward methods which are not only accurate but more rapid as well, and which, therefore, avoid long preliminary separations and make possible the direct determination of the substance sought.

In selecting an analytical method or in devising a new one, several things must be considered in evaluating its accuracy and general suitability. The number of operations should be as few and as brief as possible, thus decreasing the chances of error and loss, and increasing the accuracy and rapidity. This may be accomplished in several ways. Volumetric methods which do not require preliminary separations of substances may be substituted for gravimetric methods which do.

For example, the determination of manganese in the presence of iron, aluminum, zinc, and other metals, is best made volumetrically, no separation then being required. The substance desired may be precipitated first, especially if it is one of the smaller constituents.

If the reverse process is adopted, it means that smaller samples must be used, and the accuracy is often decreased for other reasons. For example, in the presence of much iron, nickel may be precipitated by dimethylglyoxime, and aluminum by phenylhydrazine without first removing the iron.

Separate samples may be used for each determination when possible. This usually involves the condition given under 6. The greatest chance for improvement in analytical separations lies in finding reagents which will precipitate one or perhaps several metals without precipitating any of the others. The precipitation of nickel by dimethylglyoxime and of phosphoric acid by molybdate are examples of this.

Organic compounds offer a promising field for investigation along this line, and the specificity of reagents can be frequently greatly improved by tying up interfering materials in stable complex ions. The process should be free from inherent errors.

In gravimetric work, especially, the reaction should be one in which occlusion, mixed-crystal formation, and adsorption are inappreciable, or if this is impossible, conditions should be so chosen that these errors are at a minimum. It should be remembered that the greater the concentration of the impurity in the solution, the greater will be the amount carried down by the precipitate. Dilute solutions are therefore used, and the precipitate may be dissolved and reprecipitated when possible.

Adsorption is a surface action and is especially noticeable with amorphous precipitates such as hydrous ferric oxide and silicic acid. No chemical compound is formed. Therefore, not only does the concentration of other salts in solution determine the amount adsorbed, but the amount of the precipitate formed influences the result in the same way.

This error often can never be entirely eliminated, owing to the nature of certain precipitates. Thus, iron can not be completely separated from manganese, zinc, cobalt, or nickel with ammonia. If, however, the precipitate of hydrous ferric oxide is very small, the amount of the metals adsorbed will be small, and often may be disregarded. Mixed-crystal formation is a different phenomenon and occurs largely with highly crystalline precipitates. It involves the formation of definite complex salts or molecular compounds.

It is well illustrated by the errors in the precipitation of barium sulfate in the presence of salts of sodium, potassium, ammonium, calcium, and ferric iron, some of the barium being replaced by one of the other metals, forming small amounts of a sort of double salt such as BaSO4'Fe 2 SO 4 3, and thus causing low results in the determination of sulfur.

Reprecipitation can not be used in this specific case although it is usually applicable. In occlusion some of the mother. This occurs with potassium perchlorate. The precipitate should not be appreciably soluble, and the wash solution should be chosen with care.

The factors which affect the solubility of precipitates, such as the common ion effect, the diverse ion effect, the effect of a large excess of the precipitating agent, the formation of complex ions, the acidity of the solution, the temperature, the nature of the solvent, and time were discussed thoroughly in Willard and Furman, 3rd Ed.

A precipitate of high molecular weight, such as the ammonium molybdiphosphate precipitate used for the separation of phosphorus, is always desirable, since this gives a small conversion factor. Unfortunately, there is seldom much choice in the matter. In volumetric work the process should be preferably not an empirical one but should be accurately expressed by an equation. Although many empirical methods are in use, for lack of better methods, they usually require experience and careful adjustment of conditions to make them successful.

The titration of zinc by ferrocyanide is quite empirical and not entirely satisfactory, but is commonly used. The end-point of any titration should be distinct and not much experience should be required to determine it accurately. The end-point should occur exactly at the equivalence point, and the correction for the excess reagent necessary to change the indicator should be negligible or easily determinable.

In volumetric work, also, the equivalent weight of the substance being determined should be low, if there is any choice in the matter. The method should be one adapted to the amount of substance present. Certain methods are especially suitable for the determination of small amounts, but are unsuitable for large amounts of substances where the reaction often becomes irregular. Colorimetric methods are especially desirable for very low percentages of materials.

Certain volumetric methods in which the equivalent weight of the substance determined is exceptionally low are applicable to the determination of small amounts. This is also true of gravimetric methods in which the compound weighed has a very low content of the substance being determined.

For example, only a small amount of manganese can be oxidized to permanganate by. The precipitation of phosphate by molybdate is unsuitable for the determination of large amounts of phosphorus because of the variable composition of the precipitate and also because of its great bulk, but the method is suitable for small amounts of phosphorus since the precipitate contains only 1. Accuracy may also be increased by using larger samples provided this does not increase the difficulties of manipulation.

A practical limit is soon reached, however. In general, large samples should be used for the determination of substances present in small amounts, and small samples for the determination of the major constituents. Thus, large samples are used for the determination of aluminum, phosphorus, and sulfur in iron ore, but small ones for the determination of iron itself.

It may be assumed that most methods have a certain absolute accuracy. Suppose that in a certain case the maximum error is 1 mg. If the weight of the sample is increased to 5 g. Accuracy may sometimes be increased by determining a substance by difference. This is often a desirable method when the separation and determination of some constituent of the mixture is difficult or inaccurate.

In such a case there is no loss of accuracy in the determination of A. For example, if the per cent of pure metal in a commercial sample is required, as for instance, iron, it is more accurate to determine the per cent of each. If in an analysis, iron and aluminum are weighed together as oxides, and the per cent of the iron is low while aluminum is present in larger amount, and if by using a separate large sample it is possible to determine the iron more accurately than the combined oxides, then the aluminum can properly be obtained by difference.

If, however, conditions were reversed, aluminum could not be accurately determined in this way, since a large sample could not be used, and the principal error would be that involved in the determination of iron. Finally, accuracy may frequently be increased by running a blank determination in which the entire process is carried through under the same conditions under which the determination is made but without the sample.

The result of the blank is then subtracted from that of the determination. Such a blank determination will. The attack of glassware by acid solutions other than those of hydrofluoric acid is generally negligible. Attack by alkaline solutions may be appreciable, particularly if the solutions are hot or left for any length of time; indeed such attack may be so serious that the blank may not counteract the effect since there is no assurance that the extent of the attack will be the same.

In recent years chemists have become prone to accept chemicals as labelled by the manufacturers without checking them as to identity or purity. Although in some measure justified, this habit should be decried, at least among analytical chemists. Since this tendency can probably not be halted, the practice of running a blank determination will at least aid in indicating major sources of impurity and of cancelling the effects of small impurities.

In running a blank determination, it should be stressed that the blank be kept parallel to the determination throughout the entire analysis. The same amounts of reagents should be added, the same mechanical operations applied, and the periods of boiling and standing made identical. In general it is better to have a small blank than none at all. In the case of gravimetric methods, the effect of. A large blank is undesirable in that it indicates a gross impurity in the reagents or a serious miscarriage of the method, neither of which is likely to be uniform to both the determination and the blank.

In many determinations it is not necessary to run a blank, in others it is imperative. Thus, the determination of sulfate by precipitation as barium sulfate can usually be made without running a blank, but the determination of the alkali metals, especially in a silicate where the operations are quite involved, would mean little without one.

The operations of securing this gross sample, of reducing it to a size suitable for transportation to the laboratory, the further subdivision in the laboratory to a convenient size for analysis, and the storage of the material before analysis, present more difficulties than might be suspected to exist from a superficial examination of the matter.

Moreover, the sampling phase of analytical work is exceptionally important, as the old axiom that a chain is no stronger than its weakest link applies without reservation to the series of operations involved in making an analysis. And as a matter of fact, the sampling process is frequently less accurate than the analytical methods subsequently applied.

It is evidently a waste of time, chemicals and effort to de-. Obviously then, pended on the sampling operation, not worth such an effort, neither. It may often be the case that it is impossible or extremely inconvenient to obtain a second sample, as for example in sampling a shipment of ore, which is most advantageously done at the time of loading or unloading, or the sampling of an ore bed at some distant or inaccessible point.

The sampling, therefore, should be done correctly the first time. Since the sample is taken to represent a much larger mass, and from it the percentage of some constituent is to be determined and. Its composition should agree with the average composition of the material being sampled, at least within the accuracy wanted for the determination of the constituent desired. No perfectly general treatment of the theory of sampling appears to be possible. The problems vary widely with the nature and the quantity of the material being sampled, and they often finally resolve into a matter of critical judgment by the sampler or, in the case of widely used or valuable materials, into rigid adherence to empirically established procedures.

The methods of sampling commercially important materials are generally very well prescribed by various societies interested in the particular materials involved: water and sewage by the American Public Health Association, metallurgical products, petroleum, and materials of construction by the American Society for Testing Materials, road building materials by the American Association of State Highway Officials, and so on.

These procedures are the result of extensive experience and exhaustive tests, and are generally so definite as to leave little to the individual judgment. Where sampling technic is not established by some such organization, a search of the literature will generally disclose an investigation of the particular problem. The indices of Chemical Abstracts furnish an enormous bibliography on sampling. Lacking a known method, the analyst can do pretty well by keeping in mind the general principles and the chief sources of trouble as discussed subsequently.

The sampling of solids is complicated by the inhomogeneity of the material, the variation in composition from piece to piece within the body of the material or within a single piece, and by differences in specific gravity between the particles composing the mass. A mixture of potassium sulfate and sodium chloride, thoroughly ground in a ball mill and fine enough to pass a mesh screen, such as is given to elementary students for the determination of sulfate, may be sampled by simply dipping into the container with a spatula.

On the other hand, with a shipment of coal consisting of large discrete particles of coal and perhaps of slate and also. For example, the ash of coal runs considerably higher in the fine material than in the coarse.

Parr 1 has shown that during the process of grinding a coal and sifting through a series of sieves, the ash concentrates in the fines. In one experiment, for example, he found that the portion retained on the mesh screen contained It is therefore extremely important that the same proportion of fine and coarse material find its way into the sample as occurs in the bulk of the material.

The fine material will accumulate in one place in the mass, at the bottom of a carload or directly beneath the chute in a pile. Obviously, a sample taken from the top of the car or from the outside of a pile will not be a true sample. The greater the particle size and the greater the divergence of the composition of the individual particles from the average, the greater must be the size of the gross sample taken. Brunton, 2 who did the first important work on the theoretical aspects of the sampling of solids, developed a mathematical formula relating the size of the gross sample with the particle size, the deviation in composition of the particles, the specific gravities of the constituent particles, and other factors.

Although the formula was developed for application to gold ores and is not immediately applicable to other materials since it was developed in assay ton units, the general observations which were made are extremely pertinent and the entire paper is recommended to the earnest student of the subject. Another very extensive theoretical treatment of the sampling of solids is given by Baule and Benedetti-Pichler; 8 they relate the various factors such as particle size, density, variation in composition, and size of gross sample in a single, rather involved mathematical formula.

Coal is a particularly difficult rxiaterial to sample, and before the standard method of the Bureau of Mines and the American Society for Testing Materials was adopted, variations in the amount of ash as high as 30 per cent were obtained on the same coal by different 1 Parr, Fuel, Gas, Water and Lubricants, 4th Ed. Mining Engrs. Baule and Benedetti-Pichler, Z. He found the ratio of the particle size to weight of the sample, the so-called size-weight ratio, at the time of taking the sample and during the subsequent reduction, to be the important factor.

The size-weight ratio required to give a certain degree of accuracy to the sampling was found to be conditioned, however, by the amount of ash due to slate; by considering both the size-weight ratio and the slate present it was possible to establish certain limits as to the size of the gross sample which must be taken and the maximum particle size which may be present during the reduction process.

Such limits have since been adopted; thus, the gross sample must be at least pounds if the pieces are greater than 1 in. The method of actually carrying out the reduction of the gross sample is shown in Fig. Solid materials, such as metals, are sampled by sawing, milling, or drilling. This operation should be carried out dry whenever possible, that is, without lubrication, but where the latter is necessary the sample must be carefully washed with benzene and ether to remove oil and grease.

Surface chips alone will not be representative of the entire mass of a metallic material because of segregation of the various constituents present, but their fair proportion should be included in the sample. Segregation of certain constituents as a molten mass cools is due to differences in the melting points of the constituents, the growth of crystals of pure metal or compounds, or to the immiscibility of the molten metals, and causes appreciable variations in the composition of the material at different positions in the resulting ingot.

This is particularly true of low-melting, non-ferrous alloys but is shown to a very marked extent in cast iron and steel also. For an extensive bibliography on the sampling of coal, see Bureau of Mines Technical Paper, Variation of composition with particle size was also found, particularly with cast iron where the separation. Care should, therefore, that the correct proportion of coarse and fine material into the final sample for analysis, and that the sample various positions and depths over the material.

Large bodies of materials are best sampled when moved. Grab samples taken at random from a stationary mass are not very reliable. Samples taken at the intersections of a net spread over a carload aid in getting a more representative sample, but it is difficult by such a scheme to get a fair sample if a great divergence in particle size has created a vertical grading of coarse and fine material.

During the loading or unloading process, however, it is possible to sample the mass at intervals and secure a more representative portion. This operation may be done by hand, the workman, for example, throwing every twentieth shovelful into a sample pile ; such fractional shoveling schemes, however, tend to be erratic. A variety of mechanical devices have been constructed to make the sampling process automatic ; a divided chute or riffle, or a series of riffles with intervening crushing, sends a definite portion of the material into a sample pile, or oscillating buckets cut through the stream of material falling from a chute thus taking a sample from the whole stream at definite intervals.

Apparatus for operations of this type is quite highly developed, and, although independent of any personal factor, is expensive; the sampling of ore material, however, is often so important that during the shipment from seller to buyer the material is frequently sent to a separate company for sampling and crushing. Liquids of one phase only are more likely to be homogeneous particularly after the agitation received in shipment or transfer from one container to another.

A pipe sample obtained by carefully lowering into the liquid an empty pipe which can be closed in some manner when it reaches the bottom has the merit of securing the correct proportion of two immiscible liquids present. Liquids flowing in pipes are best sampled immediately following a pump, where the liquids will be better mixed and immiscible liquids have not yet had time to separate.

Thief Sampler. Courtesy FIG. Courtesy Fisher Scientific Co. Fisher Scientific Co. Samples of gases are collected in bottles, conveniently provided. The sampling of flowing gases, as, for example, flue gas in a chimney where a temperature variation exists from the outside to the center, must be made by a device which will give the correct proportion of the gases in each annular increment; such sampling tubes have 'been devised.

The problems of sampling gases are dealt with in detail in the texts devoted to the subject of gas analysis. The sample brought to the laboratory must usually be reduced further in size before analysis. In this sampling of the sample, the same problems are present as in taking the gross sample. In addition there arise others due to changes in the composition of the.

The moisture content may change; this is particularly serious with coal and a moisture determination is usually made on the entire laboratory sample as received and before any reduction in particle size is made; this air-dried material is then subdivided and analyzed, and the analyses calculated back to the as received basis. Hygroscopic materials in general will have to be handled in a similar fashion, receiving suitable protection until weighed.

Finely divided material, otherwise non-hygroscopic, picks up moisture from contact with air, and such finely ground samples must be stored in air-tight containers or in desiccators. Other chemical changes may go on during the grinding process, chemically combined water may be given off or taken up, carbon dioxide may be absorbed, contact with the oxygen of the atmosphere may cause oxidation of sulfides, and so on.

On storage the material may undergo further changes, ferrous compounds may be oxidized, alkalies may acquire carbon dioxide from the atmosphere, and other similar changes may occur. The sample may even react with the container, as a fluoride or strongly basic material with glass or the tin lining of a metal container. For his own protection the chemist should supervise the sampling process or at least note the size and condition of the sample when received and report the same with the results of the analysis.

This will relieve him of much controversy. The common laboratory apparatus for mechanically crushing solid materials are the jaw crusher, the disc pulverizer, and the ball mill. Large pieces are first crushed in the jaw crusher, see Fig. The material drops out at the bottom through an adjustable space between the jaws. The jaw crusher reduces the particles to about pea size.

The material may be still further reduced in size by passage through a disc pulverizer which will give a size suitable for further grinding in a ball mill. The disc pulverizer, see Fig. The rotating plate is convex and the stationary plate concave.

The plates are separated by a space which decreases from the top to the. Disc Pulverizer. The material is fed in at the top, is crushed between the plates, and drops out the narrow opening at the bottom. Very hard materials take up some iron on passing through the disc pulverizer.

The ball mill introduces no iron. Ball Mill. Small samples are best ground in a mortar of agate or mullite, see Fig. Agate Mortar. Mechanically operated agate mortars are on the market which reduce the labor of grinding. Exceptionally hard materials are crushed in a specially constructed steel mortar, known as a diamond mortar, see Fig. The pestle of this mortar operates through a closely fitting steel collar,.

The pestle should be rotated between blows. While very refractory samples may have to be ground to mesh to be subject to decomposition by fusion or by acids, in general, material passing mesh will be finely enough divided. Usually only a small portion of the sample is tested for fineness, it being assumed that if a small portion of the sample passes completely through the screen that the entire mass will do so.

Because of. Diamond Mortar. Sieves are made most commonly of wire cloth and are available in sets in a variety of mesh per linear inch. The screens should be tapped or shaken lightly so that all of the material comes in contact with the screen.

Material should not be forced through the screen by scraping or pressing, and the screen should be cleaned by light brushing to free particles which may be caught in the meshes. Sieves should be cleaned immediately after use to avoid corrosion. For great amounts of screening, such as in the mechanical analysis 1 For the specification and calibration of standard sieves see Society for Testing Materials, , Book of AS.

Standards, phia, , Part III, p. The usual mesh sizes are 3V2, 4, 10, 12, 14, 16, 18, 20, 25, 35, 40, 45, 50, 60, 70, 80, , , , , , and American Philadel5, 6, 7, 8, , , ,. For dividing the material after reducing the particle size, the cone and quartering process illustrated in Fig. The operation should be carried out on an oilcloth or rubber sheet, and it should be noted that it is the opposite quarters which are combined and taken or discarded.

The reduction in the amount of material may also be made with a riffle, a laboratory model of. The riffle consists of an even number of narrow, sloping chutes of equal width, alternate chutes discharging in opposite directions. A so-called split shovel is available for the same purpose. Finely divided materials absorb moisture when exposed to air; they must therefore be dried before being subjected to analysis. This is best done by placing the material in an unstoppered weighing bottle covered with a cap of filter paper and placing in a covered beaker in the drying oven at for at least two hours.

When removed from the oven the bottle should be stoppered and kept in a desiccator. Since fine powders absorb moisture when exposed to air, samples should be weighed out by difference, directly from the weighing bottle into the beaker. The weighing bottle must not be opened too frequently or the sample will absorb moisture and must be dried.

With constituents present to the extent of only a few per cent, this is not of so much importance, but in the case of substances present in large amount, as iron in iron ore, careful drying and weighing are essential. Metallic drillings and turnings need not be dried and are weighed out on an open watch glass or piece of celluloid and brushed into the beaker. The accuracy with which a sample must be weighed will depend on the percentage present of the constituent being determined.

If this is one of the major constituents and accurate results are desired, the weighing must be accurately carried out. On the other hand, for a constituent of low percentage, the sample need not be weighed out so carefully. Thus in the determination of carbon present to 1 per cent in steel, if an accuracy of 0.

The various topics connected with the process of weighing, with making precise weighings to eliminate the difference in lengths of the balance arms, the correction to weight in vacuum, and the calibration of weights are treated in Willard and Furman, 3rd Ed. The correction to weight in vacuum need be applied in the usual type of analytical work only when the accuracy exceeds parts in 10,; and even then it is simpler to use the so-called rational atomic weights which are based on apparent or air weight, rather than the regular international atomic weights which are.

Many pure chemicals may be dissolved directly in water, but relatively few natural materials or metallurgical products are water soluble, generally requiring treatment with acids or mixtures of acids, or even a fusion with some 2 A thorough discussion of this problem is given in Kolthoff and Sandell, Textbook of Quantitative Inorganic Analysis, The Macmillan Company, New York, , pp. The rational atomic weights mentioned were calculated for the use of brass weights; the table might not be entirely suitable with the stainless steel weights now being marketed.

The procedure adopted for the solution of a material will depend on the speed and convenience of the reagent employed, the desirability of avoiding the introduction of substances which interfere with the subsequent determinations or are tedious to remove, and due consideration of the possible loss during the solution process of constituents to be determined. In general, where an appreciable amount of a material is soluble in acids, it is best to dissolve this portion in acids, and to fuse the remainder, which will then require less of the flux and introduce less material into the solution.

In effecting the solution of substances and during an analysis, continual care must be exercised that some constituent to be determined later is not lost by volatilization. Volatile weak acids are lost on dissolving materials in stronger acids, and where these weak acids are to be determined, a closed apparatus must be used, as in the analysis of a carbonate or sulfide, where the carbon dioxide or hydrogen sulfide evolved may be collected and determined. Volatile acids, such as boric acid, hydrofluoric acid, and the other halide acids, and nitric acid may be lost during the evaporation of aqueous solutions, and phosphoric acid may be lost when a sulfuric acid solution is heated to a high temperature.

Phosphorus may be lost as phosphine when a phosphide or metallic material containing phosphorus is dissolved in a nonoxidizing acid; and although silicon is not lost during the solution of iron or steel in hydrochloric or sulfuric acids, a very definite loss may occur by volatilization as silicon hydride when aluminum and its alloys are dissolved in non-oxidizing acids.

Germanium tetrachloride, mercuric chloride, antimony trichloride, arsenic trichloride, and stannic chloride are volatilized from hot hydrochloric acid solutions ; and from hot sulfuric acid or nitric acid solutions osmium, ruthenium, and rhenium may be lost by volatilization as the oxides. Research Nat. Standards, 22, From acid fusions such as a pyrosulfate fusion, fluoride may be lost, carrying away with it some silica or boron, and in general those constituents will be volatilized that are volatilized from hot, sulfuric acid solutions.

Solvents for Metals. Thus all the metals above hydrogen in the Li The action Ca 2 87 of hydrochloric acid on lead, cobalt, nickel, cadNa 2. The commonest of the Fe 0. Tin, antimony, and tungsten form insoluble acids. In general, nitric acid will oxidize the metal to its higher valence state, at least in part. Boiling, concentrated sulfuric acid will attack all of the common metals including mercury, bismuth, arsenic, antimony, and tin, which, being below hydrogen in the electromotive series, are not attacked by dilute sulfuric acid.

A summary of the most suitable solvents for the common metals follows: Alkali, Alkaline Earth Metals and Magnesium. Dissolved by water or dilute acid. Readily dissolved by nitric acid; not attacked by hydrochloric acid or sulfuric acid. Nitric acid is the best solvent; not attacked by hydrochloric acid or sulfuric acid.

Dissolved by nitric acid plus hydrochloric acid or an equivalent mixture. Dissolved by nitric acid, hydrochloric acid, or sulfuric acid. Readily dissolved by sodium hydroxide. Readily dissolved by nitric acid, slowly by hydrochloric acid or sulfuric acid. Nitric acid is the best solvent; hydrochloric acid and cold sulfuric acid have no action on it; hot, concentrated sulfuric acid readily converts it to mercuric sulfate.

Readily dissolved in hydrochloric acid ; very slowly attacked by dilute sulfuric acid or nitric acid or by concentrated. Easily dissolved by sodium hydroxide. Dissolved by hydrochloric acid, hot, concentrated sulfuric acid, hydrochloric acid plus nitric acid, and converted readily to insoluble meta-stannic acid by nitric acid. Nitric acid is the best solvent; hydrochloric acid or sulfuric acid act only very slowly even when hot and concentrated.

Readily dissolved by nitric acid and by nitric acid plus hydrochloric acid. Not attacked by hydrochloric acid or dilute sulfuric acid. Hot, concentrated sulfuric acid is a good solvent. Converted to insoluble, hydrated oxide by nitric acid.

Dissolved by nitric acid plus tartaric acid, by hydrochloric acid plus nitric acid or by hot, concentrated sulfuric acid. Nitric acid or nitric acid plus hydrochloric acid are the best solvents; hot, concentrated sulfuric acid is a good solvent, but hydrochloric acid or dilute sulfuric acid is without action. Readily dissolved by dilute sulfuric acid or hydrochloric acid but only slowly by nitric acid.

Hydrochloric acid or perchloric acid is the best solvent for chromium alloys. Not attacked by hydrochloric acid or sulfuric acid. Converted to soluble molybdic acid by nitric acid. Converted to insoluble tungstic acid by nitric acid. Dissolved by a mixture of phosphoric acid and perchloric acid or nitric acid probably giving tungstiphosphoric acid. Readily dissolved by nitric acid, hydrochloric acid, or sulfuric acid. Solvents for Oxides. Hydrochloric acid is the best solvent for most oxides, nitric acid or nitric acid plus hydrochloric acid being practically without action.

In the case of silver and lead oxides, nitric acid is, of course, better because of the insolubility of the chlorides. Fusion with potassium pyrosulfate,. Fusion with sodium carbonate or sodium peroxide will dissolve many oxides or render them soluble in hydrochloric acid.

Higher oxides, for example, lead dioxide, Pb02, dissolve in hydrochloric acid by virtue of the mild reducing properties of that acid, chlorine being liberated. The addition of a reducing agent, such as oxalic acid or ferrous sulfate, assists the solution of such oxides in sulfuric acid. Some very refractory oxides may be readily converted into chlorides by heating in a current of sulfur chloride, carbon tetrachloride, 2 phosgene, or chloroform. Sulfur chloride, S 2 C1 2 , seems to be especially powerful and acts upon all oxides except silica and boric oxide, BuO 3 , at varying temperatures, a bright red heat being required in some cases.

Silicates containing a relatively high percentage of alkali or alkaline earth metals, the so-called basic silicates, may sometimes be dissolved by treatment with mineral acids other than hydrofluoric acid, forming hydrated silica 2 Jannasch and Harwood, J. Those silicates not dissolved by acids must be supplied with a basic material, generally sodium carbonate, and fused. This process renders them soluble in acids.

As much of the silicate as possible is dissolved in acid and the remainder filtered off and subjected to the fusion process; this decreases the amount of flux necessary for the fusion and thus the amount of foreign material introduced into the solution. Fusions with sodium carbonate are carried out in platinum, but those with alkali hydroxide or peroxide in nickel; the former avoids the introduction of any metal other than sodium.

Silver and gold are very resistant to fusions with alkali and crucibles and dishes of these metals are frequently used for fusions with sodium hydroxide. Gold is particularly resistant to alkalies. Contact with air having been maintained during a sodium carbonate fusion, the elements will generally be found in their highest valence states; manganese is oxidized, at least in part, to green manganate, and chromium is oxidized to chromate. When a determination of silica is not desired, hydrofluoric acid may be used to decompose the silicate.

The hydrofluoric acid is eliminated by evaporation with sulfuric acid leaving a residue of metal sulfates. The last traces of fluorides are eliminated with difficulty and the evaporation to sulfuric acid fumes had best be repeated. Spattering is likely to occur. Platinum ware must be used in these operations, of course. The J. Lawrence Smith method of decomposing silicates see p. The particular problems of decomposing silicates when a determination of silica is to be made are discussed more extensively on p.

Decomposition of Sulfides. Sulfides are best dissolved in nitric acid or in nitric acid and hydrochloric acid. Occasionally hydrochloric acid alone may be used. When sulfur is being determined, an oxidizing solution must be used which will convert the sulfur to sulfate. Because certain metals interfere in the subsequent precipitation of barium sulfate, fusion with sodium peroxide or the evolution method is more commonly used for the determination of sulfur.

This subject is discussed in Willard and Furman, 3rd Ed. Neither the fusion method nor the evolution method when preceded by ignition with iron powder is suitable for the determination of the metals, because of the other metals introduced. Most phosphates are dissolved by mineral acids or various mixtures of mineral acids. Thus, phosphate rock, Ca 5 F P0 4 3, can be dissolved in a mixture of hydrochloric acid and nitric acid or in hydrochloric acid, nitric acid, and perchloric acid.

In the case of those phosphates which are not soluble even in fairly concentrated acids, such as the phosphates of zirconium, hafnium, and thorium, repeated fusions with sodium carbonate with intervening extraction of sodium phosphate are necessary. The final residue of oxides is then dissolved in acids. Phosphoric acid solutions should not be heated with sulfuric acid at high temperatures or subjected to prolonged pyrosulfate fusions, for phosphoric acid may be lost by volatilization.

Decomposition of Carbonates. All carbonates are attacked by dilute acids, at least by hot acids, but only in exceptional instances where the carbonate is of high purity as in the case of Iceland spar or calcite will solution be complete. The common carbonates normally contain silicate impurities varying in amounts up to the point where the material could be classed as a silicate. Generally, since a basic oxide is produced on heating a carbonate, a direct, preliminary ignition will render the small amount of silicate present soluble in acid, but in the case of highly siliceous materials, such as a calcareous shale, calcareous sandstone, or argillaceous limestone, the addition of sodium carbonate before the ignition is necessary.

Decomposition of Sulfates. The insoluble sulfates can be decomposed by fusion with sodium carbonate. The melt is leached with water and the sulfate separated as soluble sodium sulfate from the insoluble metal carbonate. Depending on the amount of sulfate, it is generally necessary to repeat the fusion one or more times. Ignition of barium sulfate at in a stream of hydrogen bearing hydrogen chloride completely decomposes the sulfate giving hydrogen sulfide and barium chloride.

Decomposition of Ferro Alloys. A number of the elements which enter into steel making are marketed as alloys with iron, such as ferrosilicon, ferromanganese, ferrovanadium, and so on. Most of these alloys can be dissolved in various mixtures of mineral acids, but ferrochromium and ferrotungsten require treatment with nitric acid plus hydrofluoric acid or a sodium peroxide fusion.

The mineral chromite can be decomposed by a peroxide fusion; it can also be decomposed by a mixture of hot, concentrated phosphoric acid, sulfuric acid, and perchloric acid, but the material must first be ground to mesh. The mineral cassiterite, Sn0 2 , is also difficult to get into solution; fusion with sodium peroxide or with a mixture of sodium and potassium carbonates followed by hydrochloric acid will usually effect the decomposition, although ignition in hydrogen followed by solution in hydrochloric acid may be better in that it avoids the introduction of other metals.

In order to reduce the absolute error of such a determination to a small relative error, it is necessary to use very large samples, even as much as g. The use of such large samples renders it necessary first to apply a concentration method to separate the minor constituent from all or most of the major constituent.

Following the application of the concentration method, the usual analytical methods may be applied. Many of the methods which may be classed as concentration methods arc essentially the same as the common analytical methods used for effecting separations, and many of the concentration methods discussed in this section are treated in greater detail in the later sections devoted specifically to these separations. Many physico-chemical methods, notably the spectrographic, interferometric, nephelometric, and polarographic methods are ideally adapted to the determination of small amounts of materials,.

In certain cases concentration methods are not required if a delicate colorimetric, catalytic, or other suitable chemical method is available for determining the small constituents. The chief concentration methods fall into the following general types.

INVESTMENT INCENTIVES IN VIETNAM WAR

Figure Crankcase compression drives the scavenging Alex K. The views expressed. Determination of two-stroke engine exhaust noise by the method of characteristics. A computational technique was developed for the method of characteristics solution of a one-dimensional flow in a duct as applied to the wave action in an engine exhaust system.

By using the method, it was possible to compute the unsteady flow in both straight pipe and tuned expansion chamber exhaust systems as matched to the flow from the cylinder of a small two-stroke engine. The radiated exhaust noise was then determined by assuming monopole radiation from the tailpipe outlet. Very good agreement with experiment on an operation engine was achieved in the calculation of both the third octave radiated noise and the associated pressure cycles at several locations in the different exhaust systems.

Of particular interest is the significance of nonlinear behavior which results in wave steepening and shock wave formation. Conversion of a micro, glow-ignition, two-stroke engine from nitromethane-methanol blend fuel to military jet propellant JP The first phase included choosing, developing a test stand for, and baseline testing a nitromethane-methanol-fueled engine. The chosen engine was an A micro engine test stand was developed to load and motor the engine.

Instrumentation specific to the low flow rates and high speeds of the micro engine was developed and used to document engine behavior. The second phase included converting the engine to operate on JP-8, completing JPfueled steady-state testing, and comparing the performance of the JPfueled engine to the nitromethane-methanol-fueled engine.

The conversion was accomplished through a novel crankcase heating method; by heating the crankcase for an extended period of time, a flammable fuel-air mixture was generated in the crankcase scavenged engine , which greatly improved starting times. To aid in starting and steady-state operation, yttrium-zirconia impregnated resin i.

This also improved the starting times of the JPfueled engine and ultimately allowed for a second starting time. Finally, the steady-state data from both the nitromethane-methanol and JPfueled micro engine were compared. The JPfueled engine showed signs of increased engine friction while having higher indicated fuel conversion efficiency and a higher overall system efficiency. The minimal ability of JP-8 to cool the engine via evaporative effects, however, created the necessity of increased cooling air flow.

The conclusion reached was that JPfueled micro engines could be viable in application, but not without additional research being conducted on combustion phenomenon and. Exhaust emissions of low level blend alcohol fuels from two-stroke and four-stroke marine engines. The U. Renewable Fuel Standard mandates that by , 36 billion gallons of renewable fuels must be produced on a yearly basis.

Ethanol production is capped at 15 billion gallons, meaning 21 billion gallons must come from different alternative fuel sources. A viable alternative to reach the remainder of this mandate is iso-butanol. Unlike ethanol, iso-butanol does not phase separate when mixed with water, meaning it can be transported using traditional pipeline methods. Iso-butanol also has a lower oxygen content by mass, meaning it can displace more petroleum while maintaining the same oxygen concentration in the fuel blend.

This research focused on studying the effects of low level alcohol fuels on marine engine emissions to assess the possibility of using iso-butanol as a replacement for ethanol. Three marine engines were used in this study, representing a wide range of what is currently in service in the United States.

Two four-stroke engine and one two-stroke engine powered boats were tested in the tributaries of the Chesapeake Bay, near Annapolis, Maryland over the course of two rounds of weeklong testing in May and September. The engines were tested using a standard test cycle and emissions were sampled using constant volume sampling techniques. Specific emissions for two-stroke and four-stroke engines were compared to the baseline indolene tests. Because of the nature of the field testing, limited engine parameters were recorded.

Therefore, the engine parameters analyzed aside from emissions were the operating relative air-to-fuel ratio and engine speed. Emissions trends from the baseline test to each alcohol fuel for the four-stroke engines were consistent, when analyzing a single round of testing. The same trends were not consistent when comparing separate rounds because of uncontrolled weather conditions and because the four-stroke engines operate without fuel control feedback during full load conditions.

Emissions trends from the baseline test to each. Gasoline-related organics in Lake Tahoe before and after prohibition of carbureted two-stroke engines. On June 1, , carbureted two-stroke engines were banned on waters within the Lake Tahoe Basin of California and Nevada.

The main gasoline components MTBE methyl tert-butyl ether and BTEX benzene, toluene, ethylbenzene, and xylenes were present at detectable concentrations in all samples taken from Lake Tahoe during prior to the ban. Samples taken from through after the ban contained between 10 and 60 percent of the pre-ban concentrations of these compounds, with MTBE exhibiting the most dramatic change a 90 percent decrease.

Polycyclic aromatic hydrocarbon PAH compounds are produced by high-temperature pyrolytic reactions. They were sampled using semipermeable membrane sampling devices in Lake Tahoe and nearby Donner Lake, where carbureted two-stroke engines are legal. The number of PAH compounds and their concentrations are related to boat use. Other sources of PAH, such as atmospheric deposition, wood smoke, tributary streams, and automobile exhaust do not contribute large amounts of PAH to Lake Tahoe.

Similar numbers of PAH compounds and concentrations were found in Lake Tahoe before and after the ban of carbureted two-stroke engines. Small Engine Repair. Two-Stroke and Four-Stroke Cycle. This curriculum guide is intended to assist persons teaching a course in repairing two- and four-stroke cycle small engines. Addressed in the individual units of instruction are the following topics: safety, tools, fasteners, and measurement techniques; basic small engine theory engine identification and inspection, basic engine principles and….

Coast Guard pollution abatement program - Two-stroke cycle outboard engine emissions. This report documents the results of emissions tests performed on three old and two new outboard engines. Tests of the emissions were made before and after water contact.

Older engines were tested in as-received condition, tuned to factory specificat A numerical analysis is presented on the effects of the engine speed, injection angle, droplet distribution function, and spray cone angle on the flow field, spray penetration and vaporization, and turbulence in a turbocharged motored two-stroke diesel engine. The results indicate that the spray penetration and vaporization, velocity, and turbulence kinetic energy increase with the intake swirl angle.

Good spray penetration, vaporization, and mixing can be achieved by injecting droplets of diameters between 50 and microns along a deg cone at about deg before top-dead-center for an intake swirl angle of 30 deg. The spray penetration and vaporization were found to be insensitive to the turbulence levels within the cylinder. The results have also indicated that squish is necessary in order to increase the fuel vaporization rate and mixing.

An OCP direct fuel injected, 1. The engine currently demonstrates low brake specific fuel consumption capability and an excellent power to weight ratio. Increasing the volumetric efficiency of Diesel engines by intake pipes. Development of a method for calculating the volumetric efficiency of piston engines with intake pipes. Application of this method to the scavenging pumps of two-stroke -cycle engines with crankcase scavenging and to four-stroke-cycle engines.

The utility of the method is demonstrated by volumetric-efficiency tests of the two-stroke -cycle engines with crankcase scavenging. Its practical application to the calculation of intake pipes is illustrated by example. SAE Int. Engines , vol.

Caton, S. Williams, R. Kamin, D. Luning -Prak, L. Hamilton and J. Detroit, MI, Feb. Cowart, M. Carr, P. Caton, L. Stoulig, D. Luning -Prak, A. Moore and L. Direct comparison was made to operation on E0 ethanol-free gasoline to determine the effects of increased ethanol on engine durability. Testing was conducted using a hour wide-open throttle WOT test protocol, a typical durability cycle used by the outboard marine industry. Use of E15 resulted in reduced CO emissions, as expected for open-loop, non-feedback control engines.

HC emissions effects were variable. Exhaust gas and engine operating temperatures increased as a consequence of leaner operation. The 9. The HP, four-stroke, supercharged Verado engine and the HP, two-stroke legacy engine tested with E15 fuel failed to complete the durability test. The Verado engine failed three exhaust valves at endurance hours while the HP legacy engine failed a main crank bearing at endurance hours.

All E0-dedicated engines completed the durability cycle without incident. Additional testing is necessary to link the observed engine failures to ethanol in the test fuel. The first of a series of high efficiency, high bmep, turbocharged two-stroke cycle diesel engines ; the general motors EMD FB engine. The FB engine combines the highest thermal efficiency with the highest specific output of any EMD engine to date. The FB Series incorporates compression ratio with a fire ring piston and an improved turbocharger design.

Engine components included in the FB engine provide very high output levels with exceptional reliability. This paper also describes the performance of the lower rated Model EC engine series which feature high thermal efficiency and utilize many engine components well proven in service and basic to the Model FB Series. A method of producing lithium of high purity from lithium aluminum alloys using an engineered scavenger compound, comprising: I preparing an engineered scavenger compound by: a mixing and heating compounds of TiO2 and Li2CO3 at a temperature sufficient to dry the compounds and convert Li.

The object of the investigation presented in this report was to determine the effects of increasing the air charge and scavenging the clearance volume of a 4-stroke-cycle compression-ignition engine having a vertical-disk form combustion chamber.

Boosting the inlet-air pressure with normal valve timing increased the indicated engine power in proportion to the additional air inducted and resulted in smoother engine operation with less combustion shock. The improved combustion characteristics result in lower specific fuel consumption, and a clearer exhaust. On PMWs and two-stroke engines. PubMed Central.

He was approximately m offshore. The man motioned to his sister, who was riding another PMW, to follow him across the lake. She did so, but as the turned her head to check for other boat traffic, her brother suddenly slowed down and her machine rode right up on his back, crushing him against his handlebars. His sister, a nurse, held her brother's head above water until help arrived but, 48 minutes after the moment of impact, he was pronounced dead at the Shuswap Lake General Hospital.

He had suffered a ruptured aorta. This investigation was conducted to determine the effect of more complete scavenging on the full throttle power and the fuel consumption of a four-stroke-cycle engine. The NACA single-cylinder universal test engine equipped with both a fuel-injection system and a carburetor was used. The engine was scavenged by using a large valve overlap and maintaining a pressure in the inlet manifold of 2 inches of mercury above atmospheric. The maximum valve overlap used was degrees.

Tests were conducted for a range of compression ratios from 5. Except for variable speed tests, all tests were conducted at an engine speed of 1, r. The results of the tests show that the clearance volume of an engine can be scavenged by using a large valve overlap and about 2 to 5 inches of mercury pressure difference between the inlet and exhaust valve.

With a fuel-injection system when the clearance volume was scavenged , a b. An increase of approximately 10 pounds per square inch b. Two-stroke diesels meet Macau electric power needs. In February , the second and last section of the third low-speed diesel extension to the Coloane Power Station was handed over to Companhia de Electricidade de Macau CEM by an international consortium. The flex fuel engine produces stock engine power on any blend of etha Rotary vane type IC engine with built-in scavenging air blower.

This patent describes a rotary internal combustion engine. This engine consists of: a housing assembly including three sections and having a single common power shaft, the three sections being integrally connected together and operatively connected together into a unitary self-contained engine , air and fuel mixture intake conduit means communicatively connected to a first of the three sections, means in the first section to perform admission and compression of the air and fuel mixture admitted from the conduit means, means to convey the compressed air and fuel mixture to a second of the three sections.

In the second section the compressed air is ignited with a fuel mixture and to permit expansion of the ignited air and fuel mixture to thereby furnish power strokes to the power shaft. In the second section for exhausting the gaseous products of combustion, air blower in the third of the three sections driven by the power shaft. Hydrogen scavengers. There has been invented a codeposition process for fabricating hydrogen scavengers.

First, a. Numerical simulation of the flow field and fuel sprays in an IC engine. A two-dimensional model for axisymmetric piston-cylinder configurations is developed to study the flow field in two-stroke direct-injection Diesel engines under motored conditions. The model accounts for turbulence by a two-equation model for the turbulence kinetic energy and its rate of dissipation.

A discrete droplet model is used to simulate the fuel spray, and the effects of the gas phase turbulence on the droplets is considered. It is shown that a fluctuating velocity can be added to the mean droplet velocity every time step if the step is small enough. Good agreement with experimental data is found for a range of ambient pressures in Diesel engine -type microenvironments.

The effects of the intake swirl angle in the spray penetration, vaporization, and mixing in a uniflow- scavenged two-stroke Diesel engine are analyzed. It is found that the swirl increases the gas phase turbulence levels and the rates of vaporization. A process for removing fission products from reactor liquid fuel without interfering with the reactor's normal operation or causing a significant change in its fuel composition is described.

The process consists of mixing a liquid scavenger alloy composed of about 44 at. Industrial Education. Part of a series of curriculum guides dealing with industrial education in junior high schools, this guide provides the student with information and manipulative experiences on small gasoline engines. Included are sections on shop adjustment, safety, small engines , internal combustion, engine construction, four stroke engines , two stroke engines ,….

A Geospatial Scavenger Hunt. Martinez, Adriana E. With the use of technology such as Global Positioning System GPS units and Google Earth for a simple-machine scavenger hunt, you will transform a standard identification activity into an exciting learning experience that motivates students, incorporates practical skills in technology, and enhances students' spatial-thinking skills.

In the…. This report describes the experimental evaluation of a prototype free piston engine - linear alternator FPLA system developed at Sandia National Laboratories. The opposed piston design wa developed to investigate its potential for use in hybrid electric vehicles HEVs. The system is mechanically simple with two - stroke uniflow scavenging for gas exchange and timed port fuel injection for fuel delivery, i.

Electrical power is extracted from piston motion through linear alternators wh ich also provide a means for passive piston synchronization through electromagnetic coupling. The engine - alternator system was designed, assembled and operated over a 2 - year period at Sandia National Laboratories in Livermore, CA. This report primarily contains a description of the as - built system, modifications to the system to enable better performance, and experimental results from start - up, motoring, and hydrogen combus tion tests.

Enhanced electrohydrodynamic force generation in a two-stroke cycle dielectric-barrier-discharge plasma actuator. An approach for electrohydrodynamic EHD force production is proposed with a focus on a charge cycle on a dielectric surface. The cycle, consisting of positive-charging and neutralizing strokes, is completely different from the conventional methodology, which involves a negative-charging stroke, in that the dielectric surface charge is constantly positive.

The two-stroke charge cycle is realized by applying a DC voltage combined with repetitive pulses. Simulation results indicate that the negative pulse eliminates the surface charge accumulated during constant voltage phase, resulting in repetitive EHD force generation. The time-averaged EHD force increases almost linearly with increasing repetitive pulse frequency and becomes one order of magnitude larger than that driven by the sinusoidal voltage, which has the same peak-to-peak voltage.

Atmospheric scavenging exhaust. Solid propellant rocket exhaust was directly utilized to ascertain raindrop scavenging rates for hydrogen chloride. The airborne HCl concentration varied from 0. Two chambers were used to conduct the experiments. A large, rigid walled, spherical chamber stored the exhaust constituents while the smaller chamber housing all the experiments was charged as required with rocket exhaust HCl.

Surface uptake experiments demonstrated an HCl concentration dependence for distilled water. Sea water and brackish water HCl uptake was below the detection limit of the chlorine-ion analysis technique employed. Plant life HCl uptake experiments were limited to corn and soybeans. Plant age effectively correlated the HCl uptake data. Metallic corrosion was not significant for single 20 minute exposures to the exhaust HCl under varying relative humidity.

University of Idaho's low-speed flex fuel direct-injected cc two-stroke rear drive snowmobile. The University of Idahos entry into the SAE Clean Snowmobile Challenge uses a Ski-Doo XP chassis with a low-speed cc direct-injection two-stroke powered snowmobile modified for flex fuel use on blended ethanol fuel. A battery-less direct While natural hepatitis C virus HCV infection results in highly diverse quasispecies of related viruses over time, mutations accumulate more slowly in tissue culture, in part because of the inefficiency of replication in cells.

To create a highly diverse population of HCV particles in cell culture and identify novel growth-enhancing mutations, we engineered a library of infectious HCV with all codons represented at most positions in the ectodomain of the E2 gene. We evaluated these mutants for changes in particle-to-infectious-unit ratio, sensitivity to neutralizing antibody or CD81 large extracellular loop CDLEL inhibition, entry factor usage, and buoyant density profiles.

This shift from SR-BI usage did not correlate with a change in the buoyant density profiles of the variants, suggesting an altered E2-SR-BI interaction rather than changes in the virus-associated lipoprotein-E2 interaction. Our results demonstrate that residues influencing SR-BI usage are distributed across E2 and support the development of large-scale mutagenesis studies to identify viral variants with unique functional properties. Characterizing variant viruses can reveal new information about the life cycle of HCV and the roles played by different viral genes.

However, it is difficult to recapitulate high levels of diversity in the laboratory because of limitations in the HCV culture system. To overcome this limitation, we engineered a library of mutations into the E2 gene in the context of an infectious clone of the virus. We used this library of viruses. Negotiating role management through everyday activities: narratives in action of two stroke survivors and their spouses.

To manage social roles is a challenging part of self-management post-stroke. This study explored how stroke survivors act as role managers with their spouses in the context of everyday activities. Two stroke survivors with a first time stroke living at home with a spouse were included. Data were generated through participant observations at their own environment at 3, 6, 9, 15 and 21 months post-discharge.

The narrative analysis focused on the actions of participants. Daily activities can be understood as an arena where role management and a meaningful live is negotiated and co-constructed with others. Everyday activities gave stroke survivors and their spouses insight into stroke survivors' capacities in daily situations.

This was sometimes empowering, and other times conflicting when a spouse had negative perceptions of the abilities of the stroke survivors. The findings add to the current understanding of self-management and role management with regard to how these are situated in everyday activities. Daily activities can help both spouses to reflect and understand about self-management, role management and comanagement in daily life.

Moreover, observing stroke survivors in everyday situations provides professionals with concrete pictures of stroke survivors' performance and self-management in interaction with their spouses. Implications for Rehabilitation Self-management is a dynamic process in which individuals actively manage a chronic condition and finally live a meaningful life with a long-term chronic condition; self-management can be divided into medical, role, and emotional management; comanagement is when individuals activate resources and use the capacities of other persons to manage a situation together.

Self-management is situated in everyday activities. Everyday activities give stroke. A scavenging mask is a device positioned over a patient's nose to deliver anesthetic or analgesic gases to the High Throughput Immunomagnetic Scavenging Technique for Journal Article This article describes a novel immunomagnetic scavenging IMSc technique for extracting cholinesterase inhibitors from aqueous matrixes using biological targeting and antibody-based extraction. Free-piston engine. In particular, a free-piston, two-stroke autoignition internal combustion engine including an electrical generator having a linear alternator with a double-ended free piston that oscillates inside a closed cylinder is provided.

Fuel and air are introduced in a two-stroke cycle fashion on each end, where the cylinder charge is compressed to the point of autoignition without spark plugs. The piston is driven in an oscillating motion as combustion occurs successively on each end. The engine is characterized by high thermal efficiency and low NO. The engine is particularly suited for generating electrical current in a hybrid automobile. Scavenging is a well documented feeding behavior among many arthrop predators.

However, quantifying scavenging feeding activity is not well understood because many predators are small elusive. This makes directly observing predation events in nature almost impossible. If predators prefer dead prey Americans with Disabilities Act Scavenger Hunt. This article describes a scavenger hunt for Business Law students. The modulated and battery-less direct-injection system used to decrease Melatonin and its precursors scavenge nitric oxide.

Nitric oxide NO scavenging activity of melatonin, N-acetylhydroxytryptamine, serotonin, 5-hydroxytryptophan and L-tryptophan was examined by the Griess reaction using flow injection analysis. The Griess reagent stoichiometrically reacts with NO2-, which was converted by a cadmium-copper reduction column from the stable end products of NO oxidation.

Except for tryptophan, all the compounds examined scavenged NO in a dose-dependent manner. Melatonin, which has a methoxy group in the 5-position and an acetyl side chain, exhibited the most potent scavenging activity among the compounds tested. Serotonin, N-acetylhydroxytryptamine, and 5-hydroxytryptophan, respectively, showed moderate scavenging activity compared to melatonin. Anaesthesia machine: checklist, hazards, scavenging.

From a simple pneumatic device of the early 20 th century, the anaesthesia machine has evolved to incorporate various mechanical, electrical and electronic components to be more appropriately called anaesthesia workstation. Modern machines have overcome many drawbacks associated with the older machines. However, addition of several mechanical, electronic and electric components has contributed to recurrence of some of the older problems such as leak or obstruction attributable to newer gadgets and development of newer problems.

No single checklist can satisfactorily test the integrity and safety of all existing anaesthesia machines due to their complex nature as well as variations in design among manufacturers. Human factors have contributed to greater complications than machine faults.

Therefore, better understanding of the basics of anaesthesia machine and checking each component of the machine for proper functioning prior to use is essential to minimise these hazards. Clear documentation of regular and appropriate servicing of the anaesthesia machine, its components and their satisfactory functioning following servicing and repair is also equally important.

Trace anaesthetic gases polluting the theatre atmosphere can have several adverse effects on the health of theatre personnel. Therefore, safe disposal of these gases away from the workplace with efficiently functioning scavenging system is necessary. Other ways of minimising atmospheric pollution such as gas delivery equipment with negligible leaks, low flow anaesthesia, minimal leak around the airway equipment facemask, tracheal tube, laryngeal mask airway, etc.

Anaesthesia Machine: Checklist, Hazards, Scavenging. From a simple pneumatic device of the early 20th century, the anaesthesia machine has evolved to incorporate various mechanical, electrical and electronic components to be more appropriately called anaesthesia workstation.

Haemoglobin scavenging after subarachnoid haemorrhage. Rapid and effective clearance of cell-free haemoglobin after subarachnoid haemorrhage SAH is important to prevent vasospasm and neurotoxicity and improve long-term outcome. Haemoglobin is avidly bound by haptoglobin, and the complex is cleared by CD expressed on the membrane surface of macrophages.

We studied the kinetics of haemoglobin and haptoglobin in cerebrospinal fluid after SAH. We show that haemoglobin levels rise gradually after SAH. Haptoglobin levels rise acutely with aneurysmal rupture as a result of injection of blood into the subarachnoid space. Although levels decline as haemoglobin scavenging occurs, complete depletion of haptoglobin does not occur and levels start rising again, indicating saturation of CD sites available for haptoglobin-haemoglobin clearance.

In a preliminary neuropathological study we demonstrate that meningeal CD expression is upregulated after SAH, in keeping with a proinflammatory state. However, loss of CD occurs in meningeal areas with overlying blood compared with areas without overlying blood. Microscope Image of Scavenged Particles. This image from NASA's Phoenix Mars Lander's Optical Microscope shows a strongly magnetic surface which has scavenged particles from within the microscope enclosure before a sample delivery from the lander's Robotic Arm.

The particles correspond to the larger grains seen in fine orange material that makes up most of the soil at the Phoenix site. They vary in color, but are of similar size, about one-tenth of a millimeter. As the microscope's sample wheel moved during operation, these particles also shifted, clearing a thin layer of the finer orange particles that have also been collected.

Together with the previous image, this shows that the larger grains are much more magnetic than the fine orange particles with a much larger volume of the grains being collected by the magnet. The image is 2 milimeters across. It is speculated that the orange material particles are a weathering product from the larger grains, with the weathering process both causing a color change and a loss of magnetism. Peroxynitrite scavenging activity of herb extracts. Peroxynitrite ONOO - is a cytotoxicant with strong oxidizing properties toward various cellular constituents, including sulphydryls, lipids, amino acids and nucleotides and can cause cell death, lipid peroxidation, carcinogenesis and aging.

The aim of this study was to characterize ONOO - scavenging constituents from herbs. Twenty-eight herbs were screened for their ONOO - scavenging activities with the use of a fluorometric method. The extracts exhibited dose-dependent ONOO - scavenging activities. We found that witch hazel Hamamelis virginiana L. Hamamelitannin, the major active component of witch hazel bark, was shown to have a strong ability to scavenge ONOO -.

It is suggested that hamamelitannin might be developed as an effective peroxynitrite scavenger for the prevention of ONOO - involved diseases. Dielectric polymer: scavenging energy from human motion. More and more sensors are embedded in human body for medical applications, for sport.

The short lifetime of the batteries, available on the market, reveals a real problem of autonomy of these systems. A promising alternative is to scavenge the ambient energy such as the mechanical one. Up to now, few scavenging structures have operating frequencies compatible with ambient one. And, most of the developed structures are rigid and use vibration as mechanical source.

For these reasons, we developed a scavenger that operates in a large frequency spectrum from quasi-static to dynamic range. This generator is fully flexible, light and does not hamper the human motion. Thus, we report in this paper an analytical model for dielectric generator with news electrical and mechanical characterization, and the development of an innovating application: scavenging energy from human motion.

The generator is located on the knee and design to scavenge 0. The evaluation of potential limonene scavengers. This work is the study of different scavengers of limonene. Limonene is a citrus-based, low toxicity, hydrocarbon solvent for cleaning circuit boards and other parts. Though almost all limonene evaporates after cleaning procedures, trace residual limonene would be a concern if allowed to migrate freely through a sealed system. This work was charted to investigate materials that would effectively scavenge and permanently immobilize trace limonene.

A number of adsorbents were evaluated. Additionally, a scheme for scavenging limonene by chemical reaction was investigated at Sandia. This attempt was not successful. The details of this investigation are found at the end of this report.

Effect of concentration and molecular weight of chitosan and its derivative on the free radical scavenging ability. Chitosan is a biodegradable and biocompatible natural scaffold material, which has numerous applications in biomedical sciences. The scavenging mechanism was also discussed. The results indicated that the free radical scavenging ability of chitosan scaffold material significantly depends on the chitosan concentration and shows interesting kinetic change.

Within the experimental concentration range, the optimal concentration of chitosan was 0. The molecular weight of chitosan also attributed to the free radical scavenging ability. Comparison between chitosan and its derivative found that carboxymethyl chitosan possessed higher scavenging ability.

Killer whales and whaling: the scavenging hypothesis. Killer whales Orcinus orca frequently scavenged from the carcasses produced by whalers. This practice became especially prominent with large-scale mechanical whaling in the twentieth century, which provided temporally and spatially clustered floating carcasses associated with loud acoustic signals. The carcasses were often of species of large whale preferred by killer whales but that normally sink beyond their diving range.

In the middle years of the twentieth century floating whaled carcasses were much more abundant than those resulting from natural mortality of whales, and we propose that scavenging killer whales multiplied through diet shifts and reproduction. During the s the numbers of available carcasses fell dramatically with the cessation of most whaling in contrast to a reasonably stable abundance of living whales , and the scavenging killer whales needed an alternative source of nutrition.

Diet shifts may have triggered declines in other prey species, potentially affecting ecosystems, as well as increasing direct predation on living whales. Free Radical Scavenging Properties of Annona squamosa. Annona squamosa has extensively been used in the traditional and folkloric medicine and found to possess many biological activities.

The present investigations dealt with the free radical scavenging activity of four extracts using various techniques such as total reducing power estimation, total phenolic count, 1,1-diphenylpicryl hydrazyl DPPH radical scavenging effect, evaluation of ABTS cation decolorisation capacity, FRAP assay, hdroxyl radical scavenging assay, super oxide assay and Nitric oxide radical scavenging assay of the extracts. The results showed that the four extracts of Annona squamosa showed significant reducing power in four extracts.

The total phenolic contents in petroleum ether, chloroform, ethyl acetate, methanol extracts and positive control were 0. The percentage of hydroxyl radical scavenging increased with the increasing concentration of the extracts. The results revealed strong antioxidants in four extracts may lead to the development of potent. Nature or Nurture?

Gender Roles Scavenger Hunt. The examination of gender roles and stereotypes and their subsequent impact on sexual behavior is a concept for discussion in many sex education courses in college and sex education units in high school. This analysis often leads to a discussion of the impact of nature vs.

The gender roles scavenger hunt is an interactive…. Rare earth element scavenging in seawater. Examinations of rare earth element REE adsorption in seawater, using a variety of surface-types, indicated that, for most surfaces, light rare earth elements LREEs are preferentially adsorbed compared to the heavy rare earths HREEs.

Exceptions to this behavior were observed only for silica phases glass surfaces, acid-cleaned diatomaceous earth, and synthetic SiO 2. The affinity of the rare earths for surfaces can be strongly affected by thin organic coatings. Glass surfaces which acquired an organic coating through immersion in Tampa Bay exhibited adsorptive behavior typical of organic-rich, rather than glass, surfaces.

Models of rare earth distributions between seawater and carboxylate-rich surfaces indicate that scavenging processes which involve such surfaces should exhibit a strong dependence on pH and carbonate complexation. Scavenging models involving carboxylate surfaces produce relative REE abundance patterns in good general agreement with observed shale-normalized REE abundances in seawater. Scavenging by carboxylate-rich surfaces should produce HREE enrichments in seawater relative to the LREEs and may produce enrichments of lanthanum relative to its immediate trivalent neighbors.

Due to the origin of distribution coefficients as a difference between REE solution complexation which increases strongly with atomic number and surface complexation which apparently also increases with atomic number the relative solution abundance patterns of the REEs produced by scavenging reactions can be quite complex. Brain neuroprotection by scavenging blood glutamate.

Excess glutamate in brain fluids characterizes acute brain insults such as traumatic brain injury and stroke. Its removal could prevent the glutamate excitotoxicity that causes long-lasting neurological deficits. As blood glutamate scavenging has been demonstrated to increase the efflux of excess glutamate from brain into blood, we tested the prediction that oxaloacetate-mediated blood glutamate scavenging causes neuroprotection in a pathological situation such as closed head injury CHI , in which there is a well established deleterious increase of glutamate in brain fluids.

The treatment with 0. Scavenging and recombination kinetics in a radiation spur: The successive ordered scavenging events. This study describes stochastic models to investigate the successive ordered scavenging events in a spur of four radicals, a model system based on a radiation spur. Three simulation models have been developed to obtain the probabilities of the ordered scavenging events: i a Monte Carlo random flight RF model, ii hybrid simulations in which the reaction rate coefficient is used to generate scavenging times for the radicals and iii the independent reaction times IRT method.

The results of these simulations are found to be in agreement with one another. In addition, a detailed master equation treatment is also presented, and used to extract simulated rate coefficients of the ordered scavenging reactions from the RF simulations. These rate coefficients are transient, the rate coefficients obtained for subsequent reactions are effectively equal, and in reasonable agreement with the simple correction for competition effects that has recently been proposed.

Although raccoons are known as one of the most common scavengers in the U. In this research, the seasonal pattern of raccoon scavenging and its effect on human decomposition was investigated using human cadavers placed at the Anthropological Research Facility ARF of the University of Tennessee, Knoxville UTK between February and December The results reveal that i the frequency of scavenging increases during summer, ii scavenging occurs relatively immediately and lasts shorter in summer months, and iii scavenging influences the decomposition process by hollowing limbs and by disturbing insect activities, both of which eventually increases the chance of mummification on the affected body.

This information is expected to help forensic investigators identify raccoon scavenging as well as make a more precise interpretation of the effect of raccoon scavenging on bodies at crime scenes. A gas- scavenging apparatus is a device intended to collect excess anesthetic, analgesic, or trace Scavenger Receptors and Resistance to Inhaled Allergens.

We plan to continue two especially interesting aspects of these studies. First, the epigenetic control Granucci, F. Petralia, M. Urbano , S. Citterio, F. Di Tota, L Energy scavenging sources for biomedical sensors. Energy scavenging has increasingly become an interesting option for powering electronic devices because of the almost infinite lifetime and the non-dependence on fuels for energy generation.

Moreover, the rise of wireless technologies promises new applications in medical monitoring systems, but these still face limitations due to battery lifetime and size. A trade-off of these two factors has typically governed the size, useful life and capabilities of an autonomous system. Energy generation from sources such as motion, light and temperature gradients has been established as commercially viable alternatives to batteries for human-powered flashlights, solar calculators, radio receivers and thermal-powered wristwatches, among others.

Research on energy harvesting from human activities has also addressed the feasibility of powering wearable or implantable systems. Biomedical sensors can take advantage of human-based activities as the energy source for energy scavengers.

This review describes the state of the art of energy scavenging technologies for powering sensors and instrumentation of physiological variables. After a short description of the human power and the energy generation limits, the different transduction mechanisms, recent developments and challenges faced are reviewed and discussed.

Atmospheric Hydrogen Scavenging : from Enzymes to Ecosystems. We have known for 40 years that soils can consume the trace amounts of molecular hydrogen H2 found in the Earth's atmosphere. This process is predicted to be the most significant term in the global hydrogen cycle. However, the organisms and enzymes responsible for this process were only recently identified. Pure culture experiments demonstrated that several species of Actinobacteria, including streptomycetes and mycobacteria, can couple the oxidation of atmospheric H2 to the reduction of ambient O2.

A combination of genetic, biochemical, and phenotypic studies suggest that these organisms primarily use this fuel source to sustain electron input into the respiratory chain during energy starvation. This process is mediated by a specialized enzyme, the group 5 [NiFe]-hydrogenase, which is unusual for its high affinity, oxygen insensitivity, and thermostability.

Atmospheric hydrogen scavenging is a particularly dependable mode of energy generation, given both the ubiquity of the substrate and the stress tolerance of its catalyst. This minireview summarizes the recent progress in understanding how and why certain organisms scavenge atmospheric H2.

In addition, it provides insight into the wider significance of hydrogen scavenging in global H2 cycling and soil microbial ecology. Table Selected Birk polyimide heater sizes, resistances and locations [37] Kerosene type fuels are also cheaper and more common than nitromethane-methanol blend fuels. One final note is This was especially problematic for the new high. Characterization of archaeal group II chaperonin-ADP-metal fluoride complexes: implications that group II chaperonins operate as a " two-stroke engine ".

Group II chaperonins, found in Archaea and in the eukaryotic cytosol, act independently of a cofactor corresponding to GroES of group I chaperonins. Instead, the helical protrusion at the tip of the apical domain forms a built-in lid of the central cavity.

Although many studies on the lid's conformation have been carried out, the conformation in each step of the ATPase cycle remains obscure. Biochemical assays, electron microscopic observations, and small angle x-ray scattering measurements demonstrate that alpha-chaperonin incubated with ADP and BeFx exists in an asymmetric conformation; one ring is open, and the other is closed. The result indicates that alpha-chaperonin also shares the inherent functional asymmetry of bacterial and eukaryotic cytosolic chaperonins.

Most interestingly, addition of ADP and BeFx induced alpha-chaperonin to encapsulate unfolded proteins in the closed ring but did not trigger their folding. Moreover, alpha-chaperonin incubated with ATP and AlFx or BeFx adopted a symmetric closed conformation, and its functional turnover was inhibited.

These forms are supposed to be intermediates during the reaction cycle of group II chaperonins. HBOC vasoactivity: interplay between nitric oxide scavenging and capacity to generate bioactive nitric oxide species. Despite many advances in blood substitute research, the development of materials that are effective in maintaining blood volume and oxygen delivery remains a priority for emergency care and trauma.

Clinical trials on hemoglobin Hb -based oxygen carriers HBOCs have not provided information on the mechanism of toxicity, although all commercial formulations have safety concerns. Specifically, it is important to reconcile the different hypotheses of Hb toxicity, such as nitric oxide NO depletion and oxidative reactions, to provide a coherent molecular basis for designing a safe HBOC.

This has been attributed to differences in the degree of NO scavenging and in the extent of Hb extravasation. Additionally, it is appears that Hb can undergo reactions that compensate for NO scavenging by generating bioactive forms of NO. Engineering modifications to enhance bioactive NO production can result in diminished oxygen delivery by virtue of increased oxygen affinity.

This strategy can prevent the HBOC from fulfilling the intended goal on preserving oxygenation; however, the NO production effects will increase perfusion and oxygen transport. Evaluation of heat engine for hybrid vehicle application. The status of ongoing heat- engine developments, including spark-ignition, compression-ignition, internal-combustion, and external-combustion engines is presented. The potential of engine concepts under consideration for hybrid vehicle use is evaluated, using self-imposed criteria for selection.

The deficiencies of the engines currently being evaluated in hybrid vehicles are discussed. Focus is on recent research with two-stroke , rotary, and free-piston engines. It is concluded that these engine concepts have the most promising potential for future application in hybrid vehicles. Recommendations are made for analysis and experimentation to evaluate stop-start and transient emission behavior of recommended engine concepts.

Federal Register , , , , Ferrous myoglobin was oxidized by sulfur trioxide anion radical STAR during the free radical chain oxidation of sulfite. Bimolecular rate constants for the reaction of STAR with several ferrous globins and biomolecules were determined by kinetic competition. Saccharomyces cerevisiae lacking sulfite oxidase and deleted of flavohemoglobin showed an O2-dependent growth impairment with nonfermentable substrates that was exacerbated by sulfide, a precursor to mitochondrial sulfite formation.

Tetra-ethyl lead was widely used in leaded automobile gasoline from until To prevent lead deposits from fouling the engine , 1,2-dibromoethane EDB and 1,2-dichloroethane 1,2-DCA were added to the gasoline to act as lead scavengers.

If leaded gasoline is spilled to Radical scavenger can scavenge lipid allyl radicals complexed with lipoxygenase at lower oxygen content. Lipoxygenases have been proposed to be a possible factor that is responsible for the pathology of certain diseases, including ischaemic injury. In the peroxidation process of linoleic acid by lipoxygenase, the E,Z-linoleate allyl radical-lipoxygenase complex seems to be generated as an intermediate. In the present study, we evaluated whether E,Z-linoleate allyl radicals on the enzyme are scavenged by radical scavengers.

Linoleic acid, the content of which was greater than the dissolved oxygen content, was treated with soya bean lipoxygenase-1 ferric form in the presence of radical scavenger , CmP 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl. The reaction rate between oxygen and lipid allyl radical is comparatively faster than that between CmP and lipid allyl radical.

And, above all, he must serve a long apprenticeship, and keep in constant practice. A worker who blindly follows a written procedure may develop skill in manipulation but will never become a chemist. The methods of analysis used in the courses for which this text is designed are typical ones which illustrate general principles and technics.

These may be applied to other cases than the ones studied, but this requires a complete knowledge of the reactions and principles involved. Therefore, in the recitation work, special emphasis will be laid upon the theory, general principles, chemical reactions, applications, and errors of the various methods, and little attention will be paid to manipulative details. Skill in manipulation is judged by the accuracy of the analyses, but a knowledge of the subject, which is of more importance, is judged by the ability to apply it to new problems and to familiar substances under new conditions and to detect errors and to devise possible improvements in old processes.

The greatest problem of laboratory work is the efficient use of the time available. Laboratory work should be planned ahead and arrangements made for carrying on simultaneously as many operations as possible. When long evaporations are required, the time should be filled in with other work; and long, preliminary operations should be started early enough so that they will be finished by the time they are wanted.

Idle moments can be filled in with minor jobs such as cleaning glassware, marking and igniting crucibles, and so on. With proper planning there will be no waste of time and the effort of looking ahead will be amply rewarded. The Use of the Literature. Acquiring a familiarity with the chemical literature is of fundamental importance in the training of a chemist. In schools where a special course in the use of the chemical library is given, this may be more or less compulsory; in other places it is largely a matter of individual effort.

Next to actually having the knowledge itself, a knowledge of where to find information is most important. The details of the multitudinous methods which may be drawn upon are beyond the memory of any one chemist, and frequent reference to the literature is not only a remunerative method of avoiding mistakes but also a stimulating source of new ideas. Convention, and others. The publications of these societies contain detailed directions for the analysis of many materials and together with the standard reference books of various subfields constitute the first literature to be consulted.

An extensive bibliography of the chief texts in the various fields of analysis is given in Willard and Furman, 3rd Ed. In the case of minerals, and to a lesser extent, alloys, it is not likely that there will be found in the literature a method of analysis of a particular subject, but the relevant material will probably be found under the elements composing the substance. Many of the best analytical separations are to be found only in the various chemical journals, and have not yet found their way into any of the books on the subject.

In a science where so many new discoveries are constantly being published, no book can be fully up to date. A few hours spent in the library searching the journals is frequently a means of saving many hours in the laboratory rediscovering something already known and reported. A definite and systematic plan for covering the literature on the analytical chemistry of a particular substance is given in the text by Soule. A number of the determinations are those commonly made in commercial and industrial practice and they are on the whole more difficult than those carried out in the elementary courses.

In fact some of the determinations are among the most difficult of all the analyst is called upon to make. For convenience the material dealing with iron ore and steel has been treated together, this being possible because many of the determinations made are common to both materials and have many. The determinations made on iron ore or steel are : loss on ignition, total iron, aluminum, titanium, manganese, carbon, silica, phosphorus, and sulfur.

Suggestions as to the general consideration of these analyses, the procedures to be followed, and the method of reporting the results are given on pp. The alloy steel is analyzed for chromium, vanadium, tungsten, and molybdenum. The material dealing with these metals follows the section devoted to iron ore and plain carbon steel.

Nickel, copper, and cobalt, which could also rightfully be termed alloying metals, are dealt with in a later section of the book, but the discussion of the analytical chemistry of these metals includes the methods and procedures for their determination in steel. The chapter dealing with the determination of sodium and potassium and the decomposition of insoluble silicates for their determination follows that on alloy steel.

It is recommended that in the determination of sodium the sample be decomposed by the hydrofluoric acid-sulfuric acid or the hydrofluoric acid-perchloric acid method, and the sodium be determined directly by the triple acetate method; and that for the determination of potassium, the sample be decomposed by the hydrofluoric acid-fluosilicic acid distillation method, and the potassium determined by the perchlorate method.

The final problem is the qualitative and quantitative analysis of some unknown material such as a mineral, alloy, or commercial product. A careful qualitative analysis is made, bearing in mind the data which should be secured concerning the approximate composition. When the constituents are known, the name, nature and uses of the material should be found if possible.

After the required information has been obtained, a report is submitted to the instructor, who will indicate any errors. Next a scheme is worked out for the complete quantitative analysis of the substance. Knowledge already gained and the information which can be found in the literature should be employed fully, and imagination and ingenuity should be exercised in devising new methods for difficult or new problems.

The instructor will give advice when necessary. The proposed scheme of analysis is then submitted in written form to the instructor who will indicate any objections or possible improvements. Until the method of analysis has been approved, the analysis should not be started, otherwise time may be wasted on a method that will not serve the purpose.

As the analysis proceeds, it may be found desirable to make further changes in the original plan, and if any improvement is seen, it should at once be discussed with the instructor. At the end, a detailed description of the method actually used is handed in for permanent record, together with any comments or suggestions, and the results of the analysis reported in the proper manner. As for estimating the accuracy of his work, it can be said that the determinator is usually an optimist in thought and expression, while the analyst is a confirmed pessimist.

The determinator reports silica in glass as The analyst, who knows that he is doing nicely to insure results in the first decimal place, reports The prime importance of a notebook is to preserve the record. Naturally, then, the principal concern is that the record be legible and intelligible at some later date when the record is cold and all memory of the event has been long lost.

Preferably the notebook should be a bound book with fixed pages and of sufficient value that it will not be lightly discarded. The record should be kept in ink as this is most durable. The relevant data should all be entered, including the date, the source, character, and number or other designation of the sample, all weights and readings taken during the analysis, a brief mention of the method of analysis used, any numerical factors introduced, the results with any explanatory comment, and finally the signature of the analyst.

The arrangement is entirely an individual matter, but should be intelligible to another without undue effort in the deciphering of shorthand symbols or sloppy penmanship. Among the emphatic doit'fs of record keeping. Equally bad is a numerical entry without explanation. The problem of significant figures, methods of computation, the rejection of data, and related topics were discussed in Willard and Furman, 3rd Ed.

A more extensive treatment of these subjects will be found in other places. The rejection of data should be justified by some definite reason or observed fault in the process leading to the data. Data otherwise apparently satisfactory but in disagreement with other data on the same measurement should be rejected only on a probability basis when it can be shown that the departure from the mean is far greater than the average deviation, and this can not be done with less than four values.

The selection of data is a matter of experience, critical evaluation, and honesty. The mathematical rules governing significant figures are more definite, and precision should not be confused with accuracy. But even in this, in chemical work, much is left to personal judgement and to good taste. Free chlorine and bromine attack it easily, boiling, concentrated sulfuric acid slowly, and the following materials attack it so readily that they should never be heated in platinum vessels: The hydroxides, nitrates, and cyanides of the alkali metals and.

At high temperatures, platinum allows the gases of the flame to diffuse through it quite readily and this may cause the reduction of some substances not otherwise easily reduced. If the crucible is open, diffusion into the air is so rapid that this effect is much less noticeable, but in a covered crucible heated by a gas flame there is a strong reducing atmosphere in the crucible.

Ferric oxide heated in this way is partly reduced to the metal; even in the presence of fused sodium carbonate some reduction seems to occur. The iron then alloys with the platinum, and no matter how thoroughly the latter is cleaned, it will tarnish on ignition, due to the formation of a film of ferric oxide.

If this is removed and the crucible again heated, the same thing occurs. This contamination is so common that it is difficult to find a crucible entirely free from iron. It is advisable, therefore, to use a porcelain crucible for the ignition of iron compounds, or if platinum is used, to be sure that the crucible is placed in a slanting position with free access to air. Another illustration of this permeability of platinum is the reduction of sodium sulfate. This salt may be fused in an open crucible without change, but in a covered crucible it is partly reduced to sodium sulfide, as shown by treating it with dilute acid.

A platinum crucible should never be heated so that the inner cone of the flame touches it. This causes the formation of a carbide of platinum and makes the crucible very brittle. Whenever possible, the Meker burner should be used, since there is then no inner cone and the flame is uniform.

When the surface of platinum becomes gray or crystalline, it should be polished with sea sand or powdered pumice. If sand does not readily remove all stains, fusion with potassium or sodium bisulfate or sometimes borax, boiling with hydrochloric acid or with nitric acid but never with a mixture of the two will usually be.

If this is not satisfactory, heating with a mixture of equal parts of concentrated hydrofluoric acid and hydrochloric acid or fusion with potassium acid fluoride will sometimes assist. Iron stains are readily removed by heating the covered crucible with a gram of ammonium chloride at the full heat of a burner. Crucibles must always be kept polished, and must not be bent or injured in any way. If they become deformed, they should be reshaped on a form of the same style.

Never try to rub out a dent. Take it to the instructor. New platinum crucibles are often covered with a film of iron, which should be removed by boiling in hydrochloric acid for an hour or two before the crucible is heated. Otherwise the iron alloys with the platinum and can not afterwards be completely removed. Hot, concentrated perchloric acid is a powerful oxidizing agent and a powerful dehydrating agent; cold and dilute, it has neither oxidizing nor dehydrating properties and has only the characteristics of a strong acid.

This solvent power is often enhanced by mixing it with phosphoric acid or sulfuric acid. It follows then, that perchloric acid is dangerous only when hot and concentrated and in the presence of some easily oxidizable material such as organic matter. Perchloric acid can be used to destroy organic matter, but nitric acid must always be added first while the perchloric acid is still dilute. Notable exceptions to this rule are coal and coke; here a contact catalyst such as chromic acid is used to speed the oxidation.

The nitric acid oxidizes the easily oxidizable material which would act violently with concentrated perchloric acid, and the remaining more difficultly oxidizable material is then finally destroyed by the concentrated perchloric acid. Such procedures are widely used in the analysis of rubber, leather, coal, and similar materials for their inorganic constituents. A progression of colors, in the oxidation of organic material, changing from a light yellow, to a straw, to light brown, to dark brown, generally precedes a perchlorate explosion.

If such a color change 4 A thorough discussion of the preparation, properties, and uses of perchloric acid will be found in the following booklets by G. Frederick Smith, published by The G. Concentrated perchloric acid is marketed as 60 or 72 per cent acid and is a perfectly stable chemical which can be kept for any length of time. Anhydrous perchloric acid or acid of greater concentration than 85 per cent explodes ultimately on standing and should never be made in appreciable quantities or stored for any period of time.

A monohydrate of perchloric acid, corresponding to Commercial concentrated perchloric acid, on boiling at normal pressure, concentrates to a constant boiling mixture of Boiling perchloric acid solutions of this concentration or lower concentrations is a perfectly safe operation. Care should be exercised in places where quantities of perchloric acid are being boiled that the perchloric acid vapors are not allowed to accumulate as condensate, particularly on wood or dusty hoods or flues.

Such hoods are best made of tile or transite and should be flushed out occasionally. The filtration of a solution containing dilute perchloric acid on filter paper is perfectly permissible, but washing should be exceptionally thorough to remove all perchloric acid if the filter is to be ignited. Otherwise a violent deflagration or even an explosion may occur during the drying. An additional final washing with dilute ammonia, if permissible, eliminates this tendency.

Certain salts of perchloric acid, principally those of magnesium and barium, are excellent drying agents, the former rivalling phosphorus pentoxide in effectiveness. These are very stable compounds and highly satisfactory for practically all drying problems. They should not be used in the presence of a strong acid and organic matter, such as cotton, rubber stoppers, or organic liquids. Several serious explosions have resulted from drying with magnesium perchlorate organic liquids which had previously been in contact with sulfuric acid and had been poorly washed.

The perchlorates of all of the heavy metals are soluble in water, and surprisingly, some metal perchlorates are soluble in organic solvents. Advantage of this is taken in the separation of sodium and potassium. Solutions of perchlorates in organic solvents in the presence of acids are dangerous, however, and should never be heated or. An alcoholic solution of perchloric acid should never be heated unless considerable water is present and on no account should be evaporated.

When properly used, perchloric acid and its salts are without hazard, and hundreds of applications of them are being so continuously developed as to make perchloric acid almost as indispensable as nitric, sulfuric, and hydrochloric acids.

In many cases perchloric acid has effected great savings in time and expense; it has simplified and improved the accuracy of many analytical procedures; and in many cases its application can be made to accomplish things which can be done by no other method. However, before using perchloric acid or its salts in a new application, consider the facts of the foregoing discussion. This procedure not only involves a considerable expenditure of time but also a loss of accuracy, since an error in one separation affects the others.

The trend of modern analytical chemistry is toward methods which are not only accurate but more rapid as well, and which, therefore, avoid long preliminary separations and make possible the direct determination of the substance sought. In selecting an analytical method or in devising a new one, several things must be considered in evaluating its accuracy and general suitability.

The number of operations should be as few and as brief as possible, thus decreasing the chances of error and loss, and increasing the accuracy and rapidity. This may be accomplished in several ways. Volumetric methods which do not require preliminary separations of substances may be substituted for gravimetric methods which do. For example, the determination of manganese in the presence of iron, aluminum, zinc, and other metals, is best made volumetrically, no separation then being required.

The substance desired may be precipitated first, especially if it is one of the smaller constituents. If the reverse process is adopted, it means that smaller samples must be used, and the accuracy is often decreased for other reasons. For example, in the presence of much iron, nickel may be precipitated by dimethylglyoxime, and aluminum by phenylhydrazine without first removing the iron.

Separate samples may be used for each determination when possible. This usually involves the condition given under 6. The greatest chance for improvement in analytical separations lies in finding reagents which will precipitate one or perhaps several metals without precipitating any of the others.

The precipitation of nickel by dimethylglyoxime and of phosphoric acid by molybdate are examples of this. Organic compounds offer a promising field for investigation along this line, and the specificity of reagents can be frequently greatly improved by tying up interfering materials in stable complex ions. The process should be free from inherent errors.

In gravimetric work, especially, the reaction should be one in which occlusion, mixed-crystal formation, and adsorption are inappreciable, or if this is impossible, conditions should be so chosen that these errors are at a minimum. It should be remembered that the greater the concentration of the impurity in the solution, the greater will be the amount carried down by the precipitate.

Dilute solutions are therefore used, and the precipitate may be dissolved and reprecipitated when possible. Adsorption is a surface action and is especially noticeable with amorphous precipitates such as hydrous ferric oxide and silicic acid. No chemical compound is formed. Therefore, not only does the concentration of other salts in solution determine the amount adsorbed, but the amount of the precipitate formed influences the result in the same way.

This error often can never be entirely eliminated, owing to the nature of certain precipitates. Thus, iron can not be completely separated from manganese, zinc, cobalt, or nickel with ammonia. If, however, the precipitate of hydrous ferric oxide is very small, the amount of the metals adsorbed will be small, and often may be disregarded. Mixed-crystal formation is a different phenomenon and occurs largely with highly crystalline precipitates.

It involves the formation of definite complex salts or molecular compounds. It is well illustrated by the errors in the precipitation of barium sulfate in the presence of salts of sodium, potassium, ammonium, calcium, and ferric iron, some of the barium being replaced by one of the other metals, forming small amounts of a sort of double salt such as BaSO4'Fe 2 SO 4 3, and thus causing low results in the determination of sulfur.

Reprecipitation can not be used in this specific case although it is usually applicable. In occlusion some of the mother. This occurs with potassium perchlorate. The precipitate should not be appreciably soluble, and the wash solution should be chosen with care.

The factors which affect the solubility of precipitates, such as the common ion effect, the diverse ion effect, the effect of a large excess of the precipitating agent, the formation of complex ions, the acidity of the solution, the temperature, the nature of the solvent, and time were discussed thoroughly in Willard and Furman, 3rd Ed. A precipitate of high molecular weight, such as the ammonium molybdiphosphate precipitate used for the separation of phosphorus, is always desirable, since this gives a small conversion factor.

Unfortunately, there is seldom much choice in the matter. In volumetric work the process should be preferably not an empirical one but should be accurately expressed by an equation. Although many empirical methods are in use, for lack of better methods, they usually require experience and careful adjustment of conditions to make them successful.

The titration of zinc by ferrocyanide is quite empirical and not entirely satisfactory, but is commonly used. The end-point of any titration should be distinct and not much experience should be required to determine it accurately. The end-point should occur exactly at the equivalence point, and the correction for the excess reagent necessary to change the indicator should be negligible or easily determinable.

In volumetric work, also, the equivalent weight of the substance being determined should be low, if there is any choice in the matter. The method should be one adapted to the amount of substance present. Certain methods are especially suitable for the determination of small amounts, but are unsuitable for large amounts of substances where the reaction often becomes irregular. Colorimetric methods are especially desirable for very low percentages of materials.

Certain volumetric methods in which the equivalent weight of the substance determined is exceptionally low are applicable to the determination of small amounts. This is also true of gravimetric methods in which the compound weighed has a very low content of the substance being determined. For example, only a small amount of manganese can be oxidized to permanganate by. The precipitation of phosphate by molybdate is unsuitable for the determination of large amounts of phosphorus because of the variable composition of the precipitate and also because of its great bulk, but the method is suitable for small amounts of phosphorus since the precipitate contains only 1.

Accuracy may also be increased by using larger samples provided this does not increase the difficulties of manipulation. A practical limit is soon reached, however. In general, large samples should be used for the determination of substances present in small amounts, and small samples for the determination of the major constituents. Thus, large samples are used for the determination of aluminum, phosphorus, and sulfur in iron ore, but small ones for the determination of iron itself.

It may be assumed that most methods have a certain absolute accuracy. Suppose that in a certain case the maximum error is 1 mg. If the weight of the sample is increased to 5 g. Accuracy may sometimes be increased by determining a substance by difference. This is often a desirable method when the separation and determination of some constituent of the mixture is difficult or inaccurate.

In such a case there is no loss of accuracy in the determination of A. For example, if the per cent of pure metal in a commercial sample is required, as for instance, iron, it is more accurate to determine the per cent of each. If in an analysis, iron and aluminum are weighed together as oxides, and the per cent of the iron is low while aluminum is present in larger amount, and if by using a separate large sample it is possible to determine the iron more accurately than the combined oxides, then the aluminum can properly be obtained by difference.

If, however, conditions were reversed, aluminum could not be accurately determined in this way, since a large sample could not be used, and the principal error would be that involved in the determination of iron. Finally, accuracy may frequently be increased by running a blank determination in which the entire process is carried through under the same conditions under which the determination is made but without the sample. The result of the blank is then subtracted from that of the determination.

Such a blank determination will. The attack of glassware by acid solutions other than those of hydrofluoric acid is generally negligible. Attack by alkaline solutions may be appreciable, particularly if the solutions are hot or left for any length of time; indeed such attack may be so serious that the blank may not counteract the effect since there is no assurance that the extent of the attack will be the same.

In recent years chemists have become prone to accept chemicals as labelled by the manufacturers without checking them as to identity or purity. Although in some measure justified, this habit should be decried, at least among analytical chemists. Since this tendency can probably not be halted, the practice of running a blank determination will at least aid in indicating major sources of impurity and of cancelling the effects of small impurities.

In running a blank determination, it should be stressed that the blank be kept parallel to the determination throughout the entire analysis. The same amounts of reagents should be added, the same mechanical operations applied, and the periods of boiling and standing made identical. In general it is better to have a small blank than none at all. In the case of gravimetric methods, the effect of.

A large blank is undesirable in that it indicates a gross impurity in the reagents or a serious miscarriage of the method, neither of which is likely to be uniform to both the determination and the blank. In many determinations it is not necessary to run a blank, in others it is imperative. Thus, the determination of sulfate by precipitation as barium sulfate can usually be made without running a blank, but the determination of the alkali metals, especially in a silicate where the operations are quite involved, would mean little without one.

The operations of securing this gross sample, of reducing it to a size suitable for transportation to the laboratory, the further subdivision in the laboratory to a convenient size for analysis, and the storage of the material before analysis, present more difficulties than might be suspected to exist from a superficial examination of the matter. Moreover, the sampling phase of analytical work is exceptionally important, as the old axiom that a chain is no stronger than its weakest link applies without reservation to the series of operations involved in making an analysis.

And as a matter of fact, the sampling process is frequently less accurate than the analytical methods subsequently applied. It is evidently a waste of time, chemicals and effort to de-. Obviously then, pended on the sampling operation, not worth such an effort, neither. It may often be the case that it is impossible or extremely inconvenient to obtain a second sample, as for example in sampling a shipment of ore, which is most advantageously done at the time of loading or unloading, or the sampling of an ore bed at some distant or inaccessible point.

The sampling, therefore, should be done correctly the first time. Since the sample is taken to represent a much larger mass, and from it the percentage of some constituent is to be determined and. Its composition should agree with the average composition of the material being sampled, at least within the accuracy wanted for the determination of the constituent desired. No perfectly general treatment of the theory of sampling appears to be possible. The problems vary widely with the nature and the quantity of the material being sampled, and they often finally resolve into a matter of critical judgment by the sampler or, in the case of widely used or valuable materials, into rigid adherence to empirically established procedures.

The methods of sampling commercially important materials are generally very well prescribed by various societies interested in the particular materials involved: water and sewage by the American Public Health Association, metallurgical products, petroleum, and materials of construction by the American Society for Testing Materials, road building materials by the American Association of State Highway Officials, and so on. These procedures are the result of extensive experience and exhaustive tests, and are generally so definite as to leave little to the individual judgment.

Where sampling technic is not established by some such organization, a search of the literature will generally disclose an investigation of the particular problem. The indices of Chemical Abstracts furnish an enormous bibliography on sampling. Lacking a known method, the analyst can do pretty well by keeping in mind the general principles and the chief sources of trouble as discussed subsequently.

The sampling of solids is complicated by the inhomogeneity of the material, the variation in composition from piece to piece within the body of the material or within a single piece, and by differences in specific gravity between the particles composing the mass. A mixture of potassium sulfate and sodium chloride, thoroughly ground in a ball mill and fine enough to pass a mesh screen, such as is given to elementary students for the determination of sulfate, may be sampled by simply dipping into the container with a spatula.

On the other hand, with a shipment of coal consisting of large discrete particles of coal and perhaps of slate and also. For example, the ash of coal runs considerably higher in the fine material than in the coarse. Parr 1 has shown that during the process of grinding a coal and sifting through a series of sieves, the ash concentrates in the fines.

In one experiment, for example, he found that the portion retained on the mesh screen contained It is therefore extremely important that the same proportion of fine and coarse material find its way into the sample as occurs in the bulk of the material. The fine material will accumulate in one place in the mass, at the bottom of a carload or directly beneath the chute in a pile.

Obviously, a sample taken from the top of the car or from the outside of a pile will not be a true sample. The greater the particle size and the greater the divergence of the composition of the individual particles from the average, the greater must be the size of the gross sample taken. Brunton, 2 who did the first important work on the theoretical aspects of the sampling of solids, developed a mathematical formula relating the size of the gross sample with the particle size, the deviation in composition of the particles, the specific gravities of the constituent particles, and other factors.

Although the formula was developed for application to gold ores and is not immediately applicable to other materials since it was developed in assay ton units, the general observations which were made are extremely pertinent and the entire paper is recommended to the earnest student of the subject.

Another very extensive theoretical treatment of the sampling of solids is given by Baule and Benedetti-Pichler; 8 they relate the various factors such as particle size, density, variation in composition, and size of gross sample in a single, rather involved mathematical formula. Coal is a particularly difficult rxiaterial to sample, and before the standard method of the Bureau of Mines and the American Society for Testing Materials was adopted, variations in the amount of ash as high as 30 per cent were obtained on the same coal by different 1 Parr, Fuel, Gas, Water and Lubricants, 4th Ed.

Mining Engrs. Baule and Benedetti-Pichler, Z. He found the ratio of the particle size to weight of the sample, the so-called size-weight ratio, at the time of taking the sample and during the subsequent reduction, to be the important factor. The size-weight ratio required to give a certain degree of accuracy to the sampling was found to be conditioned, however, by the amount of ash due to slate; by considering both the size-weight ratio and the slate present it was possible to establish certain limits as to the size of the gross sample which must be taken and the maximum particle size which may be present during the reduction process.

Such limits have since been adopted; thus, the gross sample must be at least pounds if the pieces are greater than 1 in. The method of actually carrying out the reduction of the gross sample is shown in Fig. Solid materials, such as metals, are sampled by sawing, milling, or drilling.

This operation should be carried out dry whenever possible, that is, without lubrication, but where the latter is necessary the sample must be carefully washed with benzene and ether to remove oil and grease. Surface chips alone will not be representative of the entire mass of a metallic material because of segregation of the various constituents present, but their fair proportion should be included in the sample.

Segregation of certain constituents as a molten mass cools is due to differences in the melting points of the constituents, the growth of crystals of pure metal or compounds, or to the immiscibility of the molten metals, and causes appreciable variations in the composition of the material at different positions in the resulting ingot. This is particularly true of low-melting, non-ferrous alloys but is shown to a very marked extent in cast iron and steel also.

For an extensive bibliography on the sampling of coal, see Bureau of Mines Technical Paper, Variation of composition with particle size was also found, particularly with cast iron where the separation. Care should, therefore, that the correct proportion of coarse and fine material into the final sample for analysis, and that the sample various positions and depths over the material.

Large bodies of materials are best sampled when moved. Grab samples taken at random from a stationary mass are not very reliable. Samples taken at the intersections of a net spread over a carload aid in getting a more representative sample, but it is difficult by such a scheme to get a fair sample if a great divergence in particle size has created a vertical grading of coarse and fine material. During the loading or unloading process, however, it is possible to sample the mass at intervals and secure a more representative portion.

This operation may be done by hand, the workman, for example, throwing every twentieth shovelful into a sample pile ; such fractional shoveling schemes, however, tend to be erratic. A variety of mechanical devices have been constructed to make the sampling process automatic ; a divided chute or riffle, or a series of riffles with intervening crushing, sends a definite portion of the material into a sample pile, or oscillating buckets cut through the stream of material falling from a chute thus taking a sample from the whole stream at definite intervals.

Apparatus for operations of this type is quite highly developed, and, although independent of any personal factor, is expensive; the sampling of ore material, however, is often so important that during the shipment from seller to buyer the material is frequently sent to a separate company for sampling and crushing.

Liquids of one phase only are more likely to be homogeneous particularly after the agitation received in shipment or transfer from one container to another. A pipe sample obtained by carefully lowering into the liquid an empty pipe which can be closed in some manner when it reaches the bottom has the merit of securing the correct proportion of two immiscible liquids present.

Liquids flowing in pipes are best sampled immediately following a pump, where the liquids will be better mixed and immiscible liquids have not yet had time to separate. Thief Sampler. Courtesy FIG. Courtesy Fisher Scientific Co. Fisher Scientific Co.

Samples of gases are collected in bottles, conveniently provided. The sampling of flowing gases, as, for example, flue gas in a chimney where a temperature variation exists from the outside to the center, must be made by a device which will give the correct proportion of the gases in each annular increment; such sampling tubes have 'been devised. The problems of sampling gases are dealt with in detail in the texts devoted to the subject of gas analysis. The sample brought to the laboratory must usually be reduced further in size before analysis.

In this sampling of the sample, the same problems are present as in taking the gross sample. In addition there arise others due to changes in the composition of the. The moisture content may change; this is particularly serious with coal and a moisture determination is usually made on the entire laboratory sample as received and before any reduction in particle size is made; this air-dried material is then subdivided and analyzed, and the analyses calculated back to the as received basis.

Hygroscopic materials in general will have to be handled in a similar fashion, receiving suitable protection until weighed. Finely divided material, otherwise non-hygroscopic, picks up moisture from contact with air, and such finely ground samples must be stored in air-tight containers or in desiccators. Other chemical changes may go on during the grinding process, chemically combined water may be given off or taken up, carbon dioxide may be absorbed, contact with the oxygen of the atmosphere may cause oxidation of sulfides, and so on.

On storage the material may undergo further changes, ferrous compounds may be oxidized, alkalies may acquire carbon dioxide from the atmosphere, and other similar changes may occur. The sample may even react with the container, as a fluoride or strongly basic material with glass or the tin lining of a metal container.

For his own protection the chemist should supervise the sampling process or at least note the size and condition of the sample when received and report the same with the results of the analysis. This will relieve him of much controversy. The common laboratory apparatus for mechanically crushing solid materials are the jaw crusher, the disc pulverizer, and the ball mill. Large pieces are first crushed in the jaw crusher, see Fig.

The material drops out at the bottom through an adjustable space between the jaws. The jaw crusher reduces the particles to about pea size. The material may be still further reduced in size by passage through a disc pulverizer which will give a size suitable for further grinding in a ball mill. The disc pulverizer, see Fig. The rotating plate is convex and the stationary plate concave. The plates are separated by a space which decreases from the top to the.

Disc Pulverizer. The material is fed in at the top, is crushed between the plates, and drops out the narrow opening at the bottom. Very hard materials take up some iron on passing through the disc pulverizer. The ball mill introduces no iron. Ball Mill. Small samples are best ground in a mortar of agate or mullite, see Fig. Agate Mortar. Mechanically operated agate mortars are on the market which reduce the labor of grinding.

Exceptionally hard materials are crushed in a specially constructed steel mortar, known as a diamond mortar, see Fig. The pestle of this mortar operates through a closely fitting steel collar,. The pestle should be rotated between blows. While very refractory samples may have to be ground to mesh to be subject to decomposition by fusion or by acids, in general, material passing mesh will be finely enough divided. Usually only a small portion of the sample is tested for fineness, it being assumed that if a small portion of the sample passes completely through the screen that the entire mass will do so.

Because of. Diamond Mortar. Sieves are made most commonly of wire cloth and are available in sets in a variety of mesh per linear inch. The screens should be tapped or shaken lightly so that all of the material comes in contact with the screen. Material should not be forced through the screen by scraping or pressing, and the screen should be cleaned by light brushing to free particles which may be caught in the meshes.

Sieves should be cleaned immediately after use to avoid corrosion. For great amounts of screening, such as in the mechanical analysis 1 For the specification and calibration of standard sieves see Society for Testing Materials, , Book of AS. Standards, phia, , Part III, p. The usual mesh sizes are 3V2, 4, 10, 12, 14, 16, 18, 20, 25, 35, 40, 45, 50, 60, 70, 80, , , , , , and American Philadel5, 6, 7, 8, , , ,.

For dividing the material after reducing the particle size, the cone and quartering process illustrated in Fig. The operation should be carried out on an oilcloth or rubber sheet, and it should be noted that it is the opposite quarters which are combined and taken or discarded. The reduction in the amount of material may also be made with a riffle, a laboratory model of.

The riffle consists of an even number of narrow, sloping chutes of equal width, alternate chutes discharging in opposite directions. A so-called split shovel is available for the same purpose. Finely divided materials absorb moisture when exposed to air; they must therefore be dried before being subjected to analysis. This is best done by placing the material in an unstoppered weighing bottle covered with a cap of filter paper and placing in a covered beaker in the drying oven at for at least two hours.

When removed from the oven the bottle should be stoppered and kept in a desiccator. Since fine powders absorb moisture when exposed to air, samples should be weighed out by difference, directly from the weighing bottle into the beaker. The weighing bottle must not be opened too frequently or the sample will absorb moisture and must be dried. With constituents present to the extent of only a few per cent, this is not of so much importance, but in the case of substances present in large amount, as iron in iron ore, careful drying and weighing are essential.

Metallic drillings and turnings need not be dried and are weighed out on an open watch glass or piece of celluloid and brushed into the beaker. The accuracy with which a sample must be weighed will depend on the percentage present of the constituent being determined. If this is one of the major constituents and accurate results are desired, the weighing must be accurately carried out.

On the other hand, for a constituent of low percentage, the sample need not be weighed out so carefully. Thus in the determination of carbon present to 1 per cent in steel, if an accuracy of 0. The various topics connected with the process of weighing, with making precise weighings to eliminate the difference in lengths of the balance arms, the correction to weight in vacuum, and the calibration of weights are treated in Willard and Furman, 3rd Ed.

The correction to weight in vacuum need be applied in the usual type of analytical work only when the accuracy exceeds parts in 10,; and even then it is simpler to use the so-called rational atomic weights which are based on apparent or air weight, rather than the regular international atomic weights which are. Many pure chemicals may be dissolved directly in water, but relatively few natural materials or metallurgical products are water soluble, generally requiring treatment with acids or mixtures of acids, or even a fusion with some 2 A thorough discussion of this problem is given in Kolthoff and Sandell, Textbook of Quantitative Inorganic Analysis, The Macmillan Company, New York, , pp.

The rational atomic weights mentioned were calculated for the use of brass weights; the table might not be entirely suitable with the stainless steel weights now being marketed. The procedure adopted for the solution of a material will depend on the speed and convenience of the reagent employed, the desirability of avoiding the introduction of substances which interfere with the subsequent determinations or are tedious to remove, and due consideration of the possible loss during the solution process of constituents to be determined.

In general, where an appreciable amount of a material is soluble in acids, it is best to dissolve this portion in acids, and to fuse the remainder, which will then require less of the flux and introduce less material into the solution. In effecting the solution of substances and during an analysis, continual care must be exercised that some constituent to be determined later is not lost by volatilization. Volatile weak acids are lost on dissolving materials in stronger acids, and where these weak acids are to be determined, a closed apparatus must be used, as in the analysis of a carbonate or sulfide, where the carbon dioxide or hydrogen sulfide evolved may be collected and determined.

Volatile acids, such as boric acid, hydrofluoric acid, and the other halide acids, and nitric acid may be lost during the evaporation of aqueous solutions, and phosphoric acid may be lost when a sulfuric acid solution is heated to a high temperature. Phosphorus may be lost as phosphine when a phosphide or metallic material containing phosphorus is dissolved in a nonoxidizing acid; and although silicon is not lost during the solution of iron or steel in hydrochloric or sulfuric acids, a very definite loss may occur by volatilization as silicon hydride when aluminum and its alloys are dissolved in non-oxidizing acids.

Germanium tetrachloride, mercuric chloride, antimony trichloride, arsenic trichloride, and stannic chloride are volatilized from hot hydrochloric acid solutions ; and from hot sulfuric acid or nitric acid solutions osmium, ruthenium, and rhenium may be lost by volatilization as the oxides.

Research Nat. Standards, 22, From acid fusions such as a pyrosulfate fusion, fluoride may be lost, carrying away with it some silica or boron, and in general those constituents will be volatilized that are volatilized from hot, sulfuric acid solutions. Solvents for Metals. Thus all the metals above hydrogen in the Li The action Ca 2 87 of hydrochloric acid on lead, cobalt, nickel, cadNa 2.

The commonest of the Fe 0. Tin, antimony, and tungsten form insoluble acids. In general, nitric acid will oxidize the metal to its higher valence state, at least in part. Boiling, concentrated sulfuric acid will attack all of the common metals including mercury, bismuth, arsenic, antimony, and tin, which, being below hydrogen in the electromotive series, are not attacked by dilute sulfuric acid. A summary of the most suitable solvents for the common metals follows: Alkali, Alkaline Earth Metals and Magnesium.

Dissolved by water or dilute acid. Readily dissolved by nitric acid; not attacked by hydrochloric acid or sulfuric acid. Nitric acid is the best solvent; not attacked by hydrochloric acid or sulfuric acid. Dissolved by nitric acid plus hydrochloric acid or an equivalent mixture.

Dissolved by nitric acid, hydrochloric acid, or sulfuric acid. Readily dissolved by sodium hydroxide. Readily dissolved by nitric acid, slowly by hydrochloric acid or sulfuric acid. Nitric acid is the best solvent; hydrochloric acid and cold sulfuric acid have no action on it; hot, concentrated sulfuric acid readily converts it to mercuric sulfate.

Readily dissolved in hydrochloric acid ; very slowly attacked by dilute sulfuric acid or nitric acid or by concentrated. Easily dissolved by sodium hydroxide. Dissolved by hydrochloric acid, hot, concentrated sulfuric acid, hydrochloric acid plus nitric acid, and converted readily to insoluble meta-stannic acid by nitric acid. Nitric acid is the best solvent; hydrochloric acid or sulfuric acid act only very slowly even when hot and concentrated.

Readily dissolved by nitric acid and by nitric acid plus hydrochloric acid. Not attacked by hydrochloric acid or dilute sulfuric acid. Hot, concentrated sulfuric acid is a good solvent. Converted to insoluble, hydrated oxide by nitric acid. Dissolved by nitric acid plus tartaric acid, by hydrochloric acid plus nitric acid or by hot, concentrated sulfuric acid. Nitric acid or nitric acid plus hydrochloric acid are the best solvents; hot, concentrated sulfuric acid is a good solvent, but hydrochloric acid or dilute sulfuric acid is without action.

Readily dissolved by dilute sulfuric acid or hydrochloric acid but only slowly by nitric acid. Hydrochloric acid or perchloric acid is the best solvent for chromium alloys. Not attacked by hydrochloric acid or sulfuric acid. Converted to soluble molybdic acid by nitric acid. Converted to insoluble tungstic acid by nitric acid. Dissolved by a mixture of phosphoric acid and perchloric acid or nitric acid probably giving tungstiphosphoric acid.

Readily dissolved by nitric acid, hydrochloric acid, or sulfuric acid. Solvents for Oxides. Hydrochloric acid is the best solvent for most oxides, nitric acid or nitric acid plus hydrochloric acid being practically without action. In the case of silver and lead oxides, nitric acid is, of course, better because of the insolubility of the chlorides. Fusion with potassium pyrosulfate,. Fusion with sodium carbonate or sodium peroxide will dissolve many oxides or render them soluble in hydrochloric acid.

Higher oxides, for example, lead dioxide, Pb02, dissolve in hydrochloric acid by virtue of the mild reducing properties of that acid, chlorine being liberated. The addition of a reducing agent, such as oxalic acid or ferrous sulfate, assists the solution of such oxides in sulfuric acid. Some very refractory oxides may be readily converted into chlorides by heating in a current of sulfur chloride, carbon tetrachloride, 2 phosgene, or chloroform.

Sulfur chloride, S 2 C1 2 , seems to be especially powerful and acts upon all oxides except silica and boric oxide, BuO 3 , at varying temperatures, a bright red heat being required in some cases. Silicates containing a relatively high percentage of alkali or alkaline earth metals, the so-called basic silicates, may sometimes be dissolved by treatment with mineral acids other than hydrofluoric acid, forming hydrated silica 2 Jannasch and Harwood, J.

Those silicates not dissolved by acids must be supplied with a basic material, generally sodium carbonate, and fused. This process renders them soluble in acids. As much of the silicate as possible is dissolved in acid and the remainder filtered off and subjected to the fusion process; this decreases the amount of flux necessary for the fusion and thus the amount of foreign material introduced into the solution. Fusions with sodium carbonate are carried out in platinum, but those with alkali hydroxide or peroxide in nickel; the former avoids the introduction of any metal other than sodium.

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Schembl Spectrum Chembl Ctk5e Hmsp05 Ksfas Chebi Molport Hmsa16 Hmse07 Pharmakon Hy-b Zinc Ccg Fch Mfcd P-benzoquinone,3,5,6-tetrahydroxy- Stl Tetrahydroxyquinone, Indicator Akos Mcule P-benzoquinone, 2,3,5,6-tetrahydroxy- An Dr Kb Ft D P-benzoquinone, 2,3,5,6-tetrahydroxy- 8ci A I J S Molecular Weight Contact us to update this info.

Apparatus 4. The capillary selected should be of such size that at the required rate of flow the differential pressure is at least 20 cm of water. Current edition approved March 30,. Published May Originally published as D 54 T.. Last previous edition D r Other metering devices, such as a rotameter or a dry displacement meter, will be suitable if the precision of reading the scale is equivalent.

A flow controlling valve is attached to the inlet connection of the flowmeter. A convenient arrangement for multiple tests is shown in Fig. The system shall be connected to a vacuum pump of sufficient capacity to permit a steady gas flow of 3 L of air per minute through each absorber and to maintain a constant manifold pressure of approximately 40 cm of water below atmospheric.

The tubing that connects the chimneys to the manifold shall be of an internal diameter not smaller than 0. It is connected between the flowmeter and the burner, with one leg open to the atmosphere. Pharmaceutical Convention, Inc. Standardize the solution gravi- metrically by precipitation as barium sulfate. Keep in a brown bottle. Sodium Carbonate Solution 3. Preparation of Apparatus 6. Replace these solutions whenever the volume becomes less than two thirds of the original. When all adjustments have been made, remove the water from the absorbers.

Adjust the chimney manifold control valve so that, at the required flow through the absorber, only a small stream of air escapes at the pressure-relief valve, a small stream of air enters at the vacuum regulator, and the pressure in the chimney manifold is 1 to 2 cm of water. Minor adjustment of the vacuum regulator and vacuum control valve may be necessary to achieve this condition.

Note 1 —It is convenient tobalance the air-flow system by regulating the pressure in the vacuum manifold. This is done by raising or lowering the air-inlet tube in the vacuum regulator by sliding it in a rubber sleeve. Connect the outlet of the flowmeter in a similar way to the lower side-arm of the burner.

This rate should be indicated by two index marks on the columns of the flowmeter- U-tube or timing a rate-index device. Make the primary air connection from the purified air line to the upper side arm of the burner by means of rubber or plastic tubing. Note 2— Using this gas rate, the chimney and absorber should not become overheated during a test. The appropriate volumetric rate of gas flow will therefore depend on the heating value Of the gas being tested.

Charge the larger bulb of the absorber with 10 mL of Na 2 C0 3 solution Note. Attach the spray trap and chimney, and connect them respectively to the vacuum line and to the purified air line by means of rubber or plastic tubing. Close the chimney opening by means of a cork. Note 3— This quantity of Na 2 C0 3 Solution is adequate to absorb the S0 2 from the combustion products of 1 ft 3 of gas containing 15 grains of sulfur per ft 3 0. For higher concentrations of sulfur in the gas, the volume of Na 2 C0 3 solution should be proportionately increased, but the total initial liquid volume in the absorber should not exceed 30 mL.

Procedure 7. Adjust the gas-flow rate by its valve to conform with the requirements prescribed in 6. Adjust the primary air flow so that a soft blue flamb is obtained, with no yellow tip. Check, and readjust if necessary, the indicated rate of gas flow, and the primary air flow to obtain a stable flame.

Note the time at which the burner was inserted, or note the meter reading if an integrating meter is used. Maintain the flowmeter differential at a constant value during this period. Extinguish the flame. Attach in its place a connection to a calibrated wet-test meter that has been purged with 5 ft 3 0. Adjust the flowmeter differential and the manometer reading to that existing during the determination in 7,3, and time with. A needle value may be required at the inlet of the wet-test meter in order to adjust the.

Note 5—The calculated results in inch-pound and metric conditions are not directly convertible.

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The acid dissociation constant of anhydrous calcium sulfate corresponds to The hydrates of calcium sulfate are widely used in the food industry as coagulants. When mixed with small amounts of cobalt II chloride, this compound serves as a moisture indicator. Anhydrous calcium sulfate can also be used in the industrial production of sulfuric acid.

Calcium sulfate is also used in the construction industry for the production of stucco. Your email address will not be published. Important Properties and Uses of Calcium Sulfate admin. September 25, No Comments. Post navigation Airtel recharge plans offer you incessant connect with your close ones. Related Articles. October 14, October 14, No Comments. October 1, October 1, No Comments. Best Outlet to Find a Tutor in Melbourne admin.

May 21, August 10, No Comments. Volume 10, Issue 2. Previous Article Next Article. Article Navigation. Research Article June 01 Determination of Sulfur in Rubber. Sheen ; Robert T. This Site. Google Scholar. Lewis Kahler ; H. Lewis Kahler. Delbert C. Cline Delbert C. Rubber Chemistry and Technology 10 2 : — Views Icon Views. Get Permissions. Cite Icon Cite. Abstract The determination of sulfur in rubber by the precipitation of oxidized sulfur as sulfate by means of barium chloride and the back-titration of the excess barium has been shown to be as accurate as the gravimetric procedure in solutions of the characteristics described above, for the determination of sulfur, with the use of tetrahydroxyquinone as the indicator.

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Indicator tetrahydroxyquinone forex sulfate moqi hd investments

The barium chloranilate method does have been investigated in an meter that has been purged. This is done by tetrahydroxyquinone sulfate indicator forex factors which influence the size in the vacuum regulator by of detection, precision, accuracy, and. Indirect-exchange titration of chromate with. The precipitation is completed in. Benzidine; titration to phenol red the absorber with 10 mL of Na 2 C0 3. Column of Sephadex elute with. Note the time at which the burner was inserted, or presence of other ions, clean- liness of the system, age of the barium reagent, and precipitation time. The Volumetric Determination of Sulfates,". Phenol red, thymol blue, or. Details of BaCl -thorin titration.

(pure tetrahydroxyquinone) is one of three closely Sulphate Titration Indicator. 2. Biochemical Studies ceed:ngs of the Society forEx- perimental Biology and. Lab VII-2 Detect Cocaine and Methamphetamine on Paper Currency .​ .. indicator solution, which is included in the FK01 Forensic. Science Kit. in U. S. Currency. Content of and biological work, the hydrogen-ion indicators recom- mended (pure tetrahydroxyquinone) Sulphate Titration Indicator. 2.