bluuebunny/crossref_metadata_2025 huggingface dataset:
Alcohols, Higher Aliphatic, Synthetic Processes
Authors: Wagner John D. , Lappin George R. , Zietz J. Richard
Published: July 2004

Higher aliphatic alcohols (C6–C18) are produced in a number of important industrial processes using petroleum‐based raw materials, eg, the Ziegler, oxo, and aldol processes. By far the largest volume synthetic alcohol is 2‐ethylhexanol, C8H18O, used mainly in production of the poly(vinyl chloride) plasticizer bis(2‐ethylhexyl) phthalate, C24H38O4, commonly called dioctyl phthalate or DOP. Other, lower volume synthetic alcohol application areas include solvents and specialty esters.
Syrups
Authors: Hebeda Ronald E.
Published: July 2004

Corn sweeteners, maple syrup, and molasses, all commercially available syrups, are concentrated solutions of carbohydrate. These products, produced for a variety of food and nonfood applications, are in some cases also available in a dry form. Corn sweeteners are prepared from hydrolyzed starch and include dextrose, high fructose corn syrup, regular corn syrup, and maltodextrin, which all have in common the raw material source, general methods of preparation, and many properties and applications. Dextrose, the common or commercial name forD‐glucose, is available as a syrup or as a pure crystalline solid. High fructose corn syrup is produced by the partial enzymatic isomerization of dextrose. Corn syrups and maltodextrins are clear, colorless, viscous liquids prepared by hydrolysis of starch to solutions of dextrose, maltose, and higher molecular weight saccharides. Maple syrup, like corn syrup, is a nutritive sweetener produced as a concentrated carbohydrate (sucrose) solution. Molasses is a syrup produced as a by‐product of sugar manufacture.
Talc
Authors: McCarthy Edward F.
Published: July 2004

Talc, a naturally occurring mineral, is a crystalline hydrous magnesium silicate. It occurs widely throughout the world, most often in association with magnesite, but pure talcs also occur. After sorting or beneficiation, it is milled or micronized to fine powders. Talc is platy, soft, inert, and generally white except when stained by iron or contaminated by other minerals. It is nonhazardous and is classified as a nuisance dust in powder form.

Talc is used in pulp and paper for pitch control, filling, and coating. It is used in ceramics for wall tile, electrical porcelains, and cordierite automotive catalyst supports. It finds application in paints for corrosion resistance, flatting, and TiO
2
extension. It is used in plastics to reinforce polypropylene and to detackify low density polyethylene film. Other markets include body and baby powders, rubber reinforcing, dusting roofing shingles, and joint compounds.
Tall Oil
Authors: Huibers Derk T. A.
Published: July 2004

Tall oil, a by‐product of kraft pulping of pine wood, is formed by acidifying black liquor soap skimmings. It consists of resin acids or rosin, fatty acids, and neutrals. Crude tall oil is an excellent source of rosin and tall oil fatty acid, an industrial‐grade oleic and linoleic acid blend. Extensive fractional distillation is required. The bulk of the neutrals, largely esters of fatty acids, sterols, resin and wax alcohols, and hydrocarbons, boil at either lower or higher temperatures than the boiling range of the fatty and resin acids.

Tall oil fatty acid is used to manufacture drying alkyd resins and dimer acids. Dimer acids are converted to noncrystalline polyamides with low softening points and transition temperatures. These polyamides find application in hot‐melt adhesives, printing ink resins, and epoxy curing agents. Rosin is used mainly in printing ink and adhesives and, to some extent, as emulsifier in the manufacture of styrene–butadiene elastomer rubber and paper size.
Fluorine Compounds, Inorganic, Tantalum
Authors: Mahmood Tariq , Lindahl Charles B.
Published: July 2004

Tantalum forms a single binary fluoride, tantalum pentafluoride. It is a white solid with a mp of 97C and bp of 229C. It is prepared by the reaction of tantalum pentachloride or oxide with anhydrous hydrogen fluoride. Tantalum pentafluoride has been used as a superacid catalyst for the conversion of CH4to gasolinerange hydrocarbons, in the manufacture of fluoride glass and fluoride glass optical fiber preforms.
Tar and Pitch
Authors: Betts W. D.
Published: July 2004

This article discusses the origins of tars and pitches from the pyrolysis of organic matter in general; those derived from coal are dealt with in detail. The physical characteristics of tars and pitch residues are summarized, as are the chemical composition of the fractions produced and the distillation processes by which they are obtained from coal tar.

Change has taken place in the twentieth century in the role of coal tar as the principal source of aromatic organic chemicals, and for road construction and surfacing, which has become an important source of components for carbon products, binders, and coating materials. Attention is drawn to the remaining chemical products of commercial importance, principally naphthalene, creosote oil, anthracene, and modest amounts of phenols and aromatic bases. There have also been a few newer uses for naphthalene and a novel purification process, as well as different requirements for pitches used as carbon binders and for the composition of creosote. Concern about the health and safety aspects of coal‐derived substances has been considered by the authorities, particularly in the European Union and directives, and regulations have been introduced to reduce risks in both the environment and workplace.
Tar Sands
Authors: Speight James G.
Published: July 2004

Tar sands (also known as oil sands and bituminous sands) are sand deposits impregnated with the dense, viscous petroleum‐like material called bitumen and are widely distributed throughout the world. Commercial methods for the recovery of bitumen from tar sand involve mining and nonmining operations. The Athabasca deposit is mineable within concepts of the economics and technology of open‐pit mining. Nonmining (
in situ
) recovery techniques using steam have not had the same degree of success for bitumen recovery but have had notable success in heavy oil reservoir operations.

The hot‐water process is the only successful commercial process in the 1990s to be applied to bitumen recovery from mined tar sand. Various process options have been tested.

The API gravity of tar sand bitumen varies greatly depending on the deposit; viscosity is very high and volatility low. The bitumen is upgraded by a combination of carbon rejection (coking) and product hydrotreating. Bitumen is converted commercially by delayed coking and fluid coking to distillate oils, coke, and light gases. The coker distillate is a partially upgraded material and is a suitable feed for hydrodesulfurization to produce a low sulfur synthetic crude oil.
Tea
Authors: Balentine Douglas A.
Published: July 2004

Tea, manufactured from the leaves ofCamellia sinensis, is an important commercial product worldwide. Tea contains polyphenolic and volatile constituents, which provide characteristic color and flavor. The respective chemistries of these compounds are reviewed, with emphasis on tea manufacturing and enzymology. The difference in composition between green and black teas is described. The technologies used for preparation of these and instant and decaffeinated teas are reviewed. The physiological effects of tea polyphenols as antioxidants and their possible role in reduction of chronic disease risk are briefly discussed. Vol. 23, pp. 746–768, 139 refs. to August 1995.
Tellurium and Tellurium Compounds
Authors: Hoffmann James E. , King Michael G. , Carapella S. C. , Oldfield J. E. , Putnam R. D.
Published: July 2004

Tellurium is the most metallic of the abundant chalcogens. In many of its chemical properties it still resembles oxygen, sulfur, and selenium.

Tellurium is produced as a by‐product at copper refineries throughout the world. The main uses for tellurium are as a free‐machining additive in both ferrous and nonferrous metallurgy (60%) in chemicals (25%), and in electrical applications such as solar cells and thermoelectrics (8%), and miscellaneous (7%). Applications of tellurium are frequently limited by the small quantities available. Tellurium and tellurium compounds generally have a low environmental impact.
Temperature Measurement
Authors: Sostmann Henry E.
Published: July 2004

Temperature is a measure of the hotness of something. For a measure to be rational, there must be agreement on a scale of numerical values defining hotness and on devices for realizing and displaying these values. The single temperature scale having an absolute basis in nature in the Kelvin thermodynamic temperature scale or absolute scale, based on principles that can be deduced from the first and second laws of thermodynamics. The most commonly used practical scale is the International Temperature Scale, on which temperatures are designated as Celsius degrees. Instruments of measure and measurements of various materials are discussed.
Textiles, Testing
Authors: Banks‐Lee Pamela , Pegram Jan
Published: July 2004

Objective and subjective methods for testing of fibers, yarns, and conventional fabrics are presented in this article. A brief discussion of testing methods for geotextiles and geomembranes is also given. Methods reviewed are mainly from ASTM and American Association of Textile Chemists and Colorists (AATCC) standards. Specific properties discussed are, for fibers, length, crimp, transverse dimensions, density, cross‐sectional shape, shrinkage, friction, optical, tensile and elastic properties, moisture absorption, and electrostatic and thermal properties; for yarn, size and number, twist, strength, evenness, friction and texture; and for conventional fabrics, construction, thickness, air permeability, strength and elongation, snag, pilling and abrasion resistance, shrinkage, thermal and moisture transmission, color and wash fastness, flammability, hand, drape, wrinkle resistance, luster, and comfort. Test methods for geotextiles and geomembranes include those for filtration and clogging, permeability, permittivity and pore size, tensile properties, degradation by ultraviolet light and temperature, abrasion, friction, and construction parameters, including mass and thickness. Where appropriate brief discussions of fiber, yarn, and fabric properties are included as they relate to the testing procedures. Testing equipment available for making particular measurements has also been given in many instances.
Thermal Pollution
Authors: Coutant Charles C.
Published: July 2004

Heat is a quantitative measure of energy that depends on the mass of an object; temperature is a measure of energy intensity. Although heat is the waste product of electricity generation, temperature is the environmental characteristic to which organisms respond. Few energy conversion processes are carried out without heat being rejected at some point in the process stream. Historically it has been more convenient as well as less costly to reject waste heat to the environment rather than to attempt significant recovery. Concern over heat rejection arose when quantities at localized sites rose dramatically as the electric utility industry shifted to water‐cooled, thermal‐electric generating stations of high unity capacity in the 1950s. Cooling techniques, risk minimization, thermal effects, prevention of mortality, maintaining ecosystem structure and function, impingement, biocides, entrainment, gas balance, cooling‐tower chemicals, human pathogens, aquaculture, open‐field agriculture, greenhouse agriculture, animal shelters, space heating, industrial process heat, and cooling reservoirs are discussed.
Enzyme Applications, Therapeutic
Authors: Jayaram Hiremagalur N. , Ahluwalia Gurpreet S. , Cooney David A.
Published: July 2004

Enzymes are used for the treatment of a broad variety of diseases by virtue of the fact that they catalyze chemical reactions with great speed and specificity. The principal therapeutic applications of enzymes are as thrombolytic agents capable of rapidly lysing the clots which cause, or contribute to, myocardial infarction, phlebitis, pulmonary embolisms, occluded catheters, and allied conditions; as oral or parenteral replacement therapy for genetic diseases attributable to a deficiency of a specific enzyme or family of enzymes; in oncology, for the control of the growth of select neoplasms or leukemias; and as antidotes to poisons or as counteragents capable of mitigating the delirious effects of toxins, etc. With the advent of DNA technology, strategies for preparing enzymes of human origin for human use have become readily available, thus circumventing the dual problems of immunogenicity and toxicity which are often encountered with enzyme‐proteins of bacterial origin. Making projections to the future, it is anticipated that therapeutic enzymes of human origin will play an increasingly important role in future strategies for controlling a variety of disease states.
Thermoelectric Energy Conversion
Authors: Skrabek E. A.
Published: July 2004

Thermoelectric energy conversion is the science of the interchange of thermal and electrical energy in simple solid‐state devices, generally heavily doped semiconductors. Thermoelectric devices can be used to generate electrical power, to refrigerate, or to transfer large amounts of heat without the use of freons or compressors or any rotating machinery. As well as providing the historical background and summaries on materials and technology, this article discusses such topics as thermoelectric effects, power generation, and cooling. It also provides summary descriptions of a number of applications of thermoelectric power supplies and coolers. These include spacecraft power supplies, remote location power systems on earth and newer commercial devices which could benefit the environment.
Thiosulfates
Authors: Bean S. L.
Published: July 2004

The thiosulfate ion has two inequivalent sulfur atoms, leading to interesting chemical properties. Thiosulfates are used primarily in photography as a fixative to dissolve undeveloped silver halide from negatives or prints. Either the sodium salt, also known as hypo, or the ammonium salt, ammo hypo, is employed in the photographic industry. The latter is also used for dechlorination of potable water and in flue gas‐desulfurization. A gold thiosulfate has been used in treatments for rheumatoid arthritis.
Tin and Tin Alloys
Authors: Gaver Charles C.
Published: July 2004

Tin is one of the world's most ancient metals. In most cases, tin is used on or in a manufactured material in small amounts, much out of proportion to the purpose it serves. Tin in some form has been associated with the economic and cultural growth of civilization. Food preservation and canning developed rapidly with the invention of tin‐coated steel; transportation and high speed machinery became a reality with the invention of tin‐base bearing metals; the casting of type metal was an important advance in printing technology; bronze alloys became weapons, tools, and architectural objects; and telecommunications and electronic equipment depend on the tin‐lead soldered joint. In modern technology, new uses of tin include the plating of protective coatings, nuclear energy, plastics and other polymers, agriculture, biochemistry, electronic packaging, and glassmaking. Physical properties, chemical properties, processing, economic aspects, specifications and analytical methods, health and safety factors, and uses of tin are discussed.
Fluorine Compounds, Inorganic, Tin
Authors: Lindahl Charles B. , Mahmood Tariq
Published: July 2004

Tin forms stannous fluoride, stannic fluoride, and fluorostannates. Stannous fluoride is a white solid with mp 215C. It is soluble in water ∼ 30–39% and up to 72–82% in anhydrous hydrogen fluoride. It is commercially prepared by the action of hydrogen fluoride on stannous oxide or metallic tin. Stannous fluoride is used widely in dentifrices and dental preparations because of its anticaries effect. Complexes of the type MSnF3, where M Rb, Cs, etc, were obtained from the molten mixture of SnF2with NaF, Rb, and CsF. Stannic fluoride is a white solid that sublimes at 705C. It can be prepared from the reaction of fluorine, chlorine trifluoride, or bromine trifluoride with tin(II) or tin(IV) compounds. It acts as a Lewis acid to form many complexes. It is used in the manufacture of glasses. Stannous fluoroborate, Sn(BF4)2, is produced in an electrochemical cell and is used in electroplating.
Tire Cord
Authors: Bhakuni Roop S. , Chawla Surendra K. , Kim D. K. , Shuttleworth D.
Published: July 2004

The development of various tire cord materials such as cotton, rayon, nylon, steel, polyester, fiber glass, and aramid used for the reinforcement of pneumatic tire is reviewed. Balanced properties developed through tailored cord–rubber composite laminates required for optimum tire performance are described. A general overview of tire cord materials and subsequent processing steps necessary for the laminate structure integrity during varying tire service conditions are presented. Typical chemical and physical properties pertinent to anisotropic cord–rubber composites are also described. Attempts to correlate cord mechanics and nonlinear viscoelastic responses of cord–rubber laminates with tire performance are reviewed. Tire cord laboratory test methods used for chemical and physical characterization are described. The importance of tire cord cost structure and its value governed by tire performance is depicted. In addition, environmental factors affecting vehicle design leading to research efforts for future tire cord materials with high strength‐to‐weight ratio is postulated.
Fluorine Compounds, Inorganic, Titanium
Authors: Meshri Dayal T.
Published: July 2004

Two stable binary fluorides of titanium have been characterized: titanium(III) fluoride and titanium(IV) fluoride. A more important material commercially is hexafluorotitanic acid which is used as a metal surface cleaning agent. Fluorotitanates are used in abrasive grinding wheels. Properties, manufacturers, and applications of the various compounds are described.
Tool Materials
Authors: Komanduri Ranga
Published: July 2004

Machining of materials using a cutting tool harder than the work material is a common manufacturing operation. Geometrically defined cutting tools are used to produce parts to specifications. Materials that use abrasives where the geometry changes continuously are outside the scope of this article, which covers mainly tool materials used in operations involving metals and their alloys. Wear on the cutting tool can be in the form of crater wear, flank wear, notch wear, plastic deformation, and cracking of the tool. A wide range of tool materials is available, including various steels, cast cobalt alloys, cast and coated carbides, cubic boron nitride, sintered polycrystalline diamond, and diamond coating on cemented carbides and ceramics. Performance capabilities of these materials vary. Tool materials in the United States have an estimated value of greater than $300 billion per year. High speed steels (HSS) and cemented carbides are the most extensively used tool materials, accounting for $2 billion in sales. Safety is of particular concern in metal‐cutting operations, and precautions should be taken for flying fragments. Future prospects for development of tool materials with superior qualities are outlined.
Trademarks
Authors: Ackerman Marc E. , Bogdanos Claudia T.
Published: July 2004

This article provides basic information on trademark rights and the procedures to be followed for securing those rights. It discusses the selection of trademarks and the advantages to obtaining federal trademark registration. The article sets forth the proper manner of trademark usage, so as to avoid a finding of abandonment or genericism of a mark. In this context, the assignment and licensing of trademarks are considered, with a focus on good will and quality control. Registration procedures, as well as the maintenance, protection, and enforcement of registrations, in the United States and foreign countries, are also treated. Issues of foreign priority are considered in connection with various international trademark treaties.
Water, Treatment of Swimming Pools, Spas, and Hot Tubs
Authors: Wojtowicz John A.
Published: July 2004

The swimming pool market has grown at an average of about 3% per year over the last 10 years. The total number of pools in 1991 was about\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${6\times 10^{6}}$\end{document}in the United States. The number of spas and hot tubs has grown rapidly since 1970, with an estimated\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${2.7\times 10^{6}}$\end{document}spas and hot tubs in 1991 in the United States in a growing market. Most swimming pools are of the recirculating type. Through filtration, chemical treatment, and dilution with rain and makeup water, the water can be reused without draining and refilling. Sanitizing chemicals must be added regularly to oxidize pool contaminants and kill and control disease‐carrying bacteria and other organisms introduced by swimmers and dirt entering the water. It is also necessary to destroy algae whose spores are carried into the water by wind and rain. The pH of pool water must be maintained within a desirable range for swimmer comfort and optimal effectiveness of chlorine sanitizers. In order to control the corrosive or scaling tendencies of pool water, it is also necessary to maintain a proper balance between pH, alkalinity, and hardness. Undesirable trace metals such as iron, manganese, or copper are sometimes found in source water or formed by corrosion of pool equipment. Unless removed, these metals discolor pool water and cause stains, especially damaging to plaster pool surfaces. Filtration of pool water is necessary for removal of suspended solids which otherwise cloud water and interfere with the disinfection process.
Analytical Methods, Trends
Authors: Montana Anthony J.
Published: July 2004

Analytical chemistry, the science of the measurement and characterization of systems, is being revolutionized by rapid advances in computer technology, microelectronics, and materials science. These developments are being driven by five factors: the quest for truly automated or intelligent instruments; ie, the continued development of multidimensional hyphenated instruments, the marriage of two instruments having complementary capabilities to facilitate the analysis of complex samples; continuous improvements in analyte detection limits; increased capabilities in data manipulation, hardware miniaturization, and remotein vivosensing, leading to instrumentation capable of both separation and specification; and the development of nondestructible, stable, field‐operable instrumentation utilizing fiber optic technology as in‐field sampling devices and for process control. It is becoming more desirable for the analytical chemist to move into the field via in‐field instruments and remote, point‐of‐use measurements.In situanalysis enables the study of key process parameters. On‐line analysis capability has already been extended to gc, lc, ms, and ftir techniques as well as to icp‐emission spectroscopy, flow injection analysis, and near‐infrared spectrophotometry. New technology developments such as on‐line Raman spectroscopy, x‐ray diffraction, and gc/lc were commercialized during the 1990s. One challenge is the migration of analytical techniques out of research and development, into quality control and process control. Another involves continued advances in smaller sample size, higher sensitivity and specificity and achieving lowered costs per analysis.
Carboxylic Acids, Trialkylacetic Acids
Authors: Keenan M. J. , Krevalis M. A.
Published: July 2004

The trialkylacetic acids, carboxylic acids with three alkyl groups on the alpha‐carbon, have been manufactured in the United States and Europe since the early 1960s. They are offered commercially by Exxon as neo acids and by Shell as Versatic Acids. The principal commercial products are the C5acid and the C10acid, although smaller quantities of other carbon number acids are also produced.

The C5acid, 2,2‐dimethylpropionic acid, also referred to as neopentanoic acid and as pivalic acid, is a solid at room temperature and undergoes reactions typical of carboxylic acids, such as formation of the acid chloride, esterification, reduction. Because of steric hindrance of the carbonyl group, reactions often proceed less readily than with straight chain acids, but once formed derivatives of neopentanoic acid are typically more resistant to hydrolysis and oxidation.

Neopentanoic acid is manufactured using variants of the Koch reaction, in which a strong acid catalyst is used in the reaction of olefin, carbon monoxide and water. Production worldwide is estimated at 15 thousand metric tons per year. Neopentanoic acid finds numerous uses in the production of polymers and resins, pharmaceuticals, agricultural chemicals, cosmetics, fuels, lubricants and transmission fluids.

The C10trialkylacetic acid, also known as neodecanoic acid and as Versatic 10, is a mixture of isomers, resulting in a material that is a liquid at room temperature. This acid undergoes the same reactions as neopentanoic acid, such as acid chloride formation and esterification. In addition, neodecanoic acid finds a large commercial use in the preparation of metal salts. The manufacturing process is the same as that used for neopentanoic acid. Production volumes of the C10acid are estimated at tens of thousands of metric tons per year.

Neodecanoic acid is used in a number of applications, including polymers, resins and coatings, adhesion promoters, metal‐working fluids, hydraulic fluids, metal‐extraction, fuels, lubricants, and electrical/electronic applications. Significant derivatives of neoacids include the glycidyl and vinyl esters. The glycidyl esters are manufactured by both Exxon and Shell, and are used as intermediates for the production of alkyds and acrylics, and as a reactive diluent for epoxy resins. The vinyl esters, manufactured by Shell, are used primarily in coatings, but also in construction, adhesives, cosmetics, and in a number of miscellaneous areas.
Deuterium and Tritium, Tritium
Authors: Katz Joseph J.
Published: July 2004

Tritium (3H or T) is the heaviest isotope of hydrogen. Unlike hydrogen or deuterium, T undergoes radioactive decay (B−, ∼ 12 yr half‐life). Thus T compounds experience radiation damage at elevated tritium levels. Tritium is produced by cosmic rays in the higher atmosphere, and by neutron capture in lithium–aluminum alloy in nuclear fission reactors. Tritium can be purified by distillation, by thermal diffusion, by diffusion through palladium‐silver‐nickel membranes, or by chromatography on coated molecular sieves. Tritium is widely used as a tracer in molecular biology experiments. Tritium is a key element in nuclear fusion, in which energy is produced by the controlled fusion of tritium with deuterium.
Fluorine Compounds, Inorganic, Tungsten
Authors: Henderson Philip B. , Woytek Andrew J.
Published: July 2004

Although several binary tungsten‐fluorine and some tungsten oxy‐fluoro compounds are known, tungsten hexafluoride is the only compound of commercial importance. The principal use of tungsten hexafluoride is for blanket and selective chemical vapor deposition of tungsten and tungsten silicide films in the manufacture of electronic devices. This article reviews the physical and chemical properties of tungsten hexafluoride, as well as its manufacture, specifications, handling, toxicity, and uses.
Tungsten and Tungsten Alloys
Authors: Penrice Thomas W.
Published: July 2004

Tungsten, discovered in 1755 and produced as a metal in 1783, is notable for having a very low vapor pressure, the highest melting point of any metal, and the highest tensile strength of any metal above 1650°C. It is used in the manufacture of high speed steels and as a metal filament in electric lamps, where it is fabricated by powder metallurgy using the Coolidge process. The largest application is in the manufacture of cemented carbide cutting tools. Tungsten is rated as a strategic material in the U.S. economy.

Tungsten occurs in a number of mineral forms, the most important being scheelite and wolframite. The beneficiation and hydrometallurgy are described, together with the principal intermediate compounds used to make the metal powder by hydrogen reduction. Technically it is possible to process compacted powder by arc or electron‐beam melting, but commercially the power metallurgy process of compaction, sintering, and working is used exclusively.

The largest reserves of ores occur in China, which has, in more recent years, become the principal source of supply not only for ores but for metal powder and intermediates at prices that have caused most U.S. mines to be closed. About 65% of tungsten usage is as tungsten carbide in cutting and mining tools. The instability of the market as well as economic and environmental factors have favored development of recycling processes. Used cutting tools can be treated with molten zinc and both tungsten carbide and cobalt binder are recovered as mixed powders after vacuum‐distillation of the zinc. It is estimated that 25% of cutting tools are recycled in this way in the United States.

Tungsten alloyed with nickel and iron is used for a range of high density compositions that find applications as counterweights in aircraft, as armor‐piercing penetrators, and for collimators and shielding in x‐ray machines. These alloys are characterized by high density and high modulus, which make them suitable for use in critical dynamic structures. Tungsten forms only a few alloys; tungsten–rhenium is important for thermocouples and as a tough lamp filament alloy. Insoluble tungsten has relatively low toxicity, but aerosols with cobalt and with impurities found in mining can have some effect and require controls of exposure level.
Ultrafiltration
Authors: Kuriyel Ralf
Published: July 2004

Ultrafiltration is a pressure‐driven filtration separation occurring on a molecular scale. Typically, a liquid including small dissolved molecules is forced through a porous membrane. Large dissolved molecules, colloids, and suspended solids that cannot pass through the pores are retained. Most ultrafiltration membranes are porous, asymmetric, polymeric structures produced by phase inversion, that is, the gelation or precipitation of a species from a soluble phase. Fouling is discussed. Electroultrafiltration, diafiltration, membrane equipment, systemization, and uses are thoroughly examined.
Units and Conversion Factors
Authors: Lukens Robert P.
Published: July 2004

The International System of Units, universally abbreviated SI, and also known as The Modern Metric System, is the dominant system of measurement units used throughout the world, with the exception of the United States.

SI was originally defined in
Le Système International d'Unités
, a publication by the International Bureau of Weights and Measures (BIPM), located in France. The present article conforms, with certain exceptions for use in the United States, to the latest revision of this document.

A brief history of the evolution of SI is included in the article, as well as a listing of its many advantages. Also included are a description of the seven base units and a number of derived units; a list of the prefixes used with SI and their proper use; a list of some non‐SI units used with SI; a list of units used temporarily with SI; and a list of units not to be used.

Some comments concerning units for mass, force, and weight; temperature; pressure and vacuum; energy and torque; nominal dimensions; and dimensionless quantities are also given. A list of rules for style and usage and an explanation of how to handle conversion and rounding are presented.
Uranium and Uranium Compounds
Authors: Whitlock Jeremy
Published: July 2004

An overview of uranium and uranium compounds with an emphasis on their relevance to chemical technology is provided. Uranium and its compounds have many uses both potential and applied, examples include nuclear fuel, radiation shielding, and kinetic energy penetrators. These uses have a substantial economic impact, the aspects of which are provided. Sections are provided which illustrate the occurrence, recovery, and radiochemistry of uranium as well as the properties and preparation of uranium metal. A broad overview of uranium coordination and organometallic compounds is also provided. Drawbacks to the application of uranium and uranium compounds in many processes include the chemical reactivity of the metal and the inherent radioactivity of uranium isotopes. As such, health and safety factors which must be taken into account while working with uranium are discussed.
Urea
Authors: Mavrovic Ivo , Shirley A. Ray , Coleman G. R. “Buck”
Published: July 2004

Urea was the first synthesis of an organic compound from an inorganic compound. Urea is prepared by the direct dehydration of ammonium carbamate at elevated temperature and pressure. At this time, 95% of all new urea plant are licensed by Snamprogetti, Stamicarbon, or Toyo Engineering. STAM utilizes the thermal stripping process while STAC and Toyo use CO
2
stripping. These processes are described in detail. Finishing processes, prilling, and granulation, as well as treatment of wastewater, are also discussed. Uses for urea include as a basis for fertilizer, in cattle‐feed as a supplement, in the manufacture of resins, glues, solvents and some medicinals. Some economic data is also given.
Clays, Uses
Authors: Murray Haydn H.
Published: July 2004

Clays and clay minerals have been and continue to be one of the more important industrial minerals. They are widely used in many facets of our society. Clays are important in geology, agriculture, construction, civil engineering, process industries, and environmental applications. Traditional applications number in the hundreds. Some of the more important include the use of kaolins in paper coating and filling, ceramics, paint, rubber, plastics, ink, catalyst preparations, and many others. The physical and chemical properties of kaolin are dependent on structure and composition and on the processing methods used to beneficiate the products. Bentonites are used in drilling fluids, as a binder for foundry sands and pelletizing iron ore, as a barrier to control fluid transport, as absorbents, as bleaching earths for edible oils, and many others. Palygorskite, sepiolite, halloysite, and common clays all have multiple applications. The physical properties of all these clays and clay minerals will be discussed in this article on uses of clays.
Vacuum Technology
Authors: Milleron Norman
Published: July 2004

Vacuum technology concerns the means to predict, effect, and control subatmospheric environments, ie, vacuum. Increasingly, each vacuum environment must be not only safe and cost‐, energy‐, and materials‐effective, but also tailored to serve use profitably. However, as of the late 1990s, the likely interactions between a dynamic endeavor and a potentially profitably serving vacuum environment may still not be straightforward. This article examines such topics as vacuum dynamics, instrumental measurement, vacuum systems and equipment, molecular transport, and problems such as gas leaks.
Vanillin
Authors: Esposito Lawrence J. , Formanek K. , Kientz G. , Mauger F. , Maureaux V. , Robert G. , Truchet F.
Published: July 2004

Vanillin is found as a natural product, glucovanillin, in vanilla beans. The extract, as such, has an inconsistent quality and its use has given way to production of synthetic vanillin, derived from catechol. It can also be obtained from lignin in sulfite wastes treated with alkali, and from guaiacol, where its impurities, by comparison, are odorless.

Physical properties, solubility data, and data about particle‐size distribution, taste and flavor, and available grades of Rhovanil Extra Pure vanillin of Rhône‐Poulenc are given. Chemical reactions such as decomposition are discussed.

Uses as a flavor enhancer in numerous food products, and as a key part of flavor compounding are mentioned. The four principal notes in flavor perception are classified to show the role played by vanillin in flavor compounding. Uses in baking, chocolate, vanillin sugar, and as a palatability enhancer in animal feed are discussed.

Use in perfumery of a vanilla‐like product is examined, with its important role in the field of aroma description. Many vanillin uses in perfumery are touched on, as are also some in flavor‐masking, pharmaceuticals, agrochemical products, and in antiultraviolet protection. Analysis and determination techniques are discussed. Vanillin in the diet shows no significant health or carcinogenic risk to humans.
Vinyl Chloride
Authors: Cowfer Joseph A. , Gorensek Maximilian B.
Published: July 2004

A brief history of the commercial development of vinyl chloride, tabulation of its physical properties, discussion of its chemical reactions, detailed descriptions of the component processes currently used for its production, economic aspects, uses, toxicity and handling precautions, and purity standards are given. Chemical reactions that vinyl chloride undergoes include polymerization, substitution at the carbon–chlorine bond, oxidation, addition, photochemistry, and pyrolysis. Important manufacturing methods are described with emphasis on the balanced process based on ethylene and chlorine feedstocks. Component processes of direct chlorination, oxychlorination, and pyrolysis of the intermediate 1,2‐dichloroethane (EDC) are described in terms of their reaction mechanisms, operating conditions, conversions and yields, and overall process integration. Oxychlorination technology comparisons are made between processes involving either fixed‐ or fluidized‐bed reactors and either air or oxygen feeds. Intermediate 1,2‐dichloroethane purification requirements are described as are by‐product handling and disposal and environmental considerations. Technology trends are also briefly discussed. Economic aspects given include production and cost of vinyl chloride monomer, a listing of U.S. producers, and current worldwide capacity. Quality standards are also presented, along with toxicity and handling precautions.
Vinyl Alcohol Polymers
Authors: Marten F. L.
Published: July 2004

Poly(vinyl alcohol) is a highly crystalline polyhydroxy polymer produced by the hydrolysis of poly(vinyl acetate) because the vinyl alcohol monomer is not available. The polymer is water‐soluble and possesses excellent tensile strength, abrasion resistance, and superior oxygen‐barrier properties. PVA has excellent emulsification and protective colloid properties. Solvent, oil, and grease resistance are matched by few other polymers.

Poly(vinyl alcohol) undergoes chemical reactions in a manner similar to other secondary polyhydroxy alcohols, and is fully biodegradable. The polymer is considered a nonhazardous material according to the American Standard for Precautionary Labeling of Hazardous Industrial Chemicals.

Industrial applications of poly(vinyl alcohol) are all based on and limited by the use of water solutions. The polymer is not considered thermoplastic as the degradation temperature is below the melting point.

Poly(vinyl alcohol) is commercially available in granular and powdered form. Grades include both fully hydrolyzed and partially hydrolyzed products. A wide variety of molecular weight and hydrolysis is commercially available.

Major end uses include textile sizing, adhesives, protective colloid for emulsion polymerization, paper coating, cement and mortar additive, poly(vinyl butyral), fibers, and films.
Vinyl Chloride Polymers
Authors: Summers James W.
Published: July 2004

PVC has a large sales volume, second only to polyethylene. Its high chlorine content provides it with a high level of combustion resistance for building products, electrical enclosures, and wire and cable insulation. PVC has a unique ability to be compounded with a wide variety of additives, making it possible to produce materials in a range from flexible elastomers (the first thermoplastic elastomers) to rigid compounds, materials that are weatherable such as for siding and windows, compounds that have stiff melts and little elastic recovery for outstanding dimensional control useful in profile extrusion, or low viscosity melts which compete effectively with ABS and PC/ABS in thin‐walled injection molding parts such as computer monitor housings.

Some PVC properties are attributed to unique morphology. The polymer precipitates from its monomer and grows into primary particles, which are later the melt flow units. Fusion into larger structures and product strength are controlled by breakdown of the grains into primary particles, by choice of additives, by amount of melting (temperature), and by number of tie molecules (molecular weight).

The main type of polymerization is the suspension process, with significant polymerization made by the mass, solution, microsuspension, and emulsion processes. In the suspension process, the polymerization takes place in droplets of monomer suspended in water. From an environmental viewpoint, PVC is over 50% chlorine and as a result, is one of the most energy‐efficient polymers. PVC is an inherent flame retardant, and acts as a marker, enabling automated equipment to sort PVC containers from other plastics in the waste stream. Vinyl is recycled by at least 170 recyclers in the United States and Canada and more than 3,500 communities accept vinyl products in their recycling programs. The analysis from 155 large‐scale, commercial incinerator facilities found no relationship between the chlorine content of waste nor the addition of PVC, and dioxin emissions from combustion processes. New requirements from the U.S. EPA make scrubbers mandatory on all incinerators and are necessary whether or not PVC is present in the waste feed.
Vinylidene Chloride Polymers
Authors: Wessling R. A. , Gibbs D. S. , Obi B. E. , Beyer D.E. , DeLassus P. T. , Howell B. A.
Published: July 2004

Vinylidene chloride is a versatile monomer used primarily for making Vinylidene chloride copolymers. These copolymers are mostly used in food packaging to provide a good barrier‐to‐mass transport. Most applications rely on the low permeation of oxygen, carbon dioxide, and water vapor. However, the polymers have also been shown to have good barrier to flavors and aromas. Thus, a barrier layer of one of these copolymers in a package structure not only prevents spoilage of the food item but prevents flavor “scalping” on the supermarket shelf. These copolymers are available in three forms. First, the resin for extrusion into film or sheet represents the largest segment. This segment includes monolayer and coextruded film and coextruded sheet. Second, a number of emulsion resins are used for solution applications. A thin layer is coated onto a substrate. Third, copolymer latexes are used for paper coatings, etc. The coatings from solution or latex dry clear. Vinylidene chloride homopolymer does not have commercial application because its melting temperature is too high to permit extrusion without degradation, and it does not dissolve in a suitable solvent for coating.
Vitamin A
Authors: Van Arnum Susan D.
Published: July 2004

An overview of the history of vitamin A is presented from its use in ancient times to structural elucidation in the 1930s. A description of commercially important retinoids and carotenoids is given. Owing to the presence of an extended polyene chain, the physical and chemical properties of these compounds are dominated by this feature and these characteristics are discussed. The current industrial syntheses of vitamin A as well as the syntheses of β‐carotene are compared and contrasted. A common element to the industrial preparation of vitamin A is that these processes have a common intermediate β‐ionone. Their differences lie in methodology to elaborate the side chain and in methods of preparation of β‐ionone. Biological aspects of vitamin A and β‐carotene in animal and plant systems are reviewed as well as important dietary sources of these substances. Analytical methodology is presented.
Vitamin E
Authors: Casani Robert
Published: July 2004

A brief history of the vitamin from its discovery to the present is given. An overview of synthetic approaches to vitamin E is presented starting with the original work in the late 1930s. A review of the literature indicates emphasis on the development of the synthesis of the trimethylhydroquinone intermediate and of the critical condensation reaction to tocopherol. The occurrence of vitamin E and compounds with vitamin E activity in natural sources along with the isolation of natural forms of vitamin E from vegetable oil sources has been summarized. The greater prevalence of compounds with vitamin E activity in vegetable sources compared to animal sources is shown. A brief review of the physiological role of vitamin E is given. In addition to research on its historical role in reproduction, a discussion of recent activity on the antioxidant properties is presented. The uses and commercial forms of vitamin E are discussed. Its role in animal feed fortification, food preservation, and polymer applications is summarized. The traditional colorimetric analysis for vitamin E in foods, feeds, and product forms is reviewed. More modern chromatographic methods for various sample matrices are presented.
Vitamin B12
Authors: Scott John W.
Published: July 2004

Vitamin B12is the generic name for a closely related group of substances of microbial origin. The compounds are octahedral cobalt corrin complexes varying primarily in one axial ligand. Vitamin B12functions as coenzyme in a number of rearrangement reactions, as well as in the methylation of homocysteine to methionine. A total synthesis of cyanocobalamin has been achieved. Commercial production, however, is entirely by fermentation of species such asPseudomonas dentrificans.
Wastes, Industrial
Authors: Eckenfelder W. Wesley
Published: July 2004

Wastewater management is discussed in detail. A spectrum of parameters and characterization of wastewater is covered. Wastewater treatments include minimization of waste as a primary measure, followed by chemical and biological treatments. These treatments include equalization, neutralization, removal of oil and grease, suspended solids removal, heavy metals, removal of volatile organics, stripping, sorption, biodegradation, and nutrient removal. Alternative biological treatments include lagoon and aerated lagoons, activated sludge, fixed‐film processes, rotating biological contactors, and anaerobic treatment. Also given is information on advanced wastewater treatments, ie, chemical oxidation and adsorption, sludge handling, and disposal. A section on storm‐water control concludes the article.