bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulatory Agencies, Survey
Authors: Passow Nancy R.
Published: July 2004

Because of updates and reauthorization, regulations covering health, safety, and environmental issues change continuously and specifications can become outdated. Regulatory agencies provide assistance regarding the laws and regulations of these issues. The two main federal agencies involved in the protection of human health and the environment are the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA). Primary laws covered by the EPA are the Clean Air Act Amendments (CAAA); the Clean Water Act (CWA); Resource Conservation and Recovery Act (RCRA); Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); Toxic Substances Control Act (TSCA); and the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The principal function of OSHA is the protection of people in the workplace. Other functions of regulatory agencies, eg, agriculture, commerce, defense, and energy, are discussed.
Fibers, Survey
Authors: Rebenfeld Ludwig
Published: July 2004

This survey provides an overview of fiber consumption trends, and of the structure and properties of those fibers that are used in the production of typical apparel, household, and industrial textiles. Both naturally occurring fibers, such as cotton and wool, and synthetic fibers are discussed. The three principal types of fibrous materials (woven, knitted, and nonwoven) are defined and described, as is the relative importance of various geometric, physical, and chemical properties of fibers. Particular attention is given to mechanical properties, since fibers can be viewed as elements of construction from which complex three‐dimensional structures are manufactured. Finally, this survey provides an overview of the important molecular and macromolecular characteristics of those polymers that are fiber‐forming. These considerations extend to natural vegetable fibers, where the principal polymer is cellulose, and to fabricated fibers based either on modification of cellulose or on synthetic polymers, among which polyamides, polyesters, polyolefins, and polyacrylonitrile are the most important.
Chlorocarbons and Chlorohydrocarbons, Survey
Authors: Marshall Kenric A.
Published: July 2004

An overview of chlorinated hydrocarbon production is provided. The properties of selected products are discussed, as is the chemistry important to their use and manufacture. Typical manufacturing processes are described. Demand and pricing for the major products are listed, along with the factors influencing consumption trends.
Photochemical Technology, Survey
Authors: Sahyun M. R. V.
Published: July 2004

Photochemical technology is utilized industrially for organic and polymer synthesis, for thin‐film fabrication, and for the manufacture of laser video and compact audio disks. Photochemistry is also employed in medicine. Applications have grown as light sources and corresponding instrumentation have been developed, and the processes involved have become better understood. The photophysical basis of energy transfer is presented. Photohalogenation of aliphatic hydrocarbons, including the photochlorination of poly(vinyl chloride) is discussed as is the synthesis of vitamin D and techniques such as laser photochemical vapor deposition for semiconductor epitaxy. Polymer‐based technologies such as stereolithography is presented. The field of phototherapy, including the use of laser‐activated sensitizers for treatment of cancers and the use of light therapy for infants, is discussed.
Sweeteners
Authors: Lee Thomas D.
Published: July 2004

Many of the available sweeteners that generate fewer calories than sugar do not have all the advantages of sugar. The six commercially available nonnutritive sweeteners are aspartame, acesulfame‐K, saccharin, cyclamate, stevioside, and glycyrrhizin. Two others, sucralose and alitame, are being developed. The sweetness potency, taste profile, chemical and physical properties, as well as synthesis and usage profiles of these compounds are reviewed. Important decomposition products are discussed.

The structure–activity relationship of dipeptide sweeteners and sweetness synergy imparted by sweetener blends are presented, as are discussions of sweetener receptors, sweetness enhancers/inducers, sweetness inhibitors, and sweet‐taste transduction mechanisms. Some sweeteners are most likely to be used only as flavor modifiers. A list of lesser known sweeteners is included.
Silicon Compounds, Synthetic Inorganic Silicates
Authors: Falcone James S.
Published: July 2004

Synthetic alkali silicates containing alkali metal oxides are manufactured as liquids or glasses that readily dissolve in water to form alkaline solutions. These silicates contain a complex mixture of polymeric species that vary as a function of alkali‐to‐silica ratio of the material, solution concentration, impurities content, and pH. The polymer chemistry of silicates influences the properties and function of these materials in a variety of applications, spanning much of the chemical process industry. Uses are in detergency, water treatment, mineral beneficiation, bleach stabilization, enhanced oil recovery, and as a raw material for the syntheses of silica sols, gels and precipitates, zeolites, clays, and other siliceous materials. The speciation and structure of silicates, studied using a broad variety of analytical methods, are discussed. Properties of the synthetic alkali silicates that determine their function in a variety of commercial applications are presented. Economic, manufacturing, regulatory, and environmental aspects of silicate production and usage are reviewed.
Tanks and Pressure Vessels
Authors: Myers Philip
Published: July 2004

Tanks are used in chemical process industry not only to store gases, liquids, and solids, but also as vessels for unit operations and as reactors. The use of tanks as liquid containers, whether at atmospheric or low pressure, above or below ground, is emphasized. Physical properties important to stored liquids are reviewed. The main components of tanks, including roof and bottoms designs, materials of construction, and tank selection criteria are presented. Special engineering considerations of both low temperature and heated tanks as well as high pressure tanks (pressure vessels) are discussed, as are federal regulations pertaining to tanks. Tank spills and leaks, and also their causes, detection, and prevention, are discussed.
Tantalum and Tantalum Compounds
Authors: Lambert John B.
Published: July 2004

Tantalum, discovered in 1802, was not produced in significant quantities until the invention of the solid tantalum capacitor. This tough, ductile, silvery gray metal is used primarily in electronic capacitors and a variety of chemical manufacturing applications. Corrosion resistance and the ability to support a stable anodic oxide film make tantalum an excellent material for prosthetics and biomedical devices as well as a substrate for capacitor dielectric. Tantalum is a prime candidate for reaction vessel liners, heat exchangers, and heat shields. The most important tantalum compound is potassium heptafluorotantalate, from which tantalum metal is formed. Other commercially significant tantalum compounds are used in cemented carbides for cutting tools, cermets, waveguides, and other optical and electronic devices.
Technical Service
Authors: Reid Austin H.
Published: July 2004

Technical service in the chemical industry is designed to provide timely and professional information and support to downstream customers regarding chemical products and their uses. Examples of the various tasks pertinent to contemporary technical service efforts are given; information on the structure of technical service organization, training of personnel, participation in technical societies, and trade associations are discussed. The part played by technical service and the product development function, and the uses of computer and other electronic technologies in technical service are included.
Terpenoids
Authors: Bledsoe James O.
Published: July 2004

Terpenes are found in essential oils and oleoresins of plants. Terpenes found in turpentine are used as raw materials for the commercial synthesis of a wide range of aroma chemicals. Uses for the monoterpenes are covered in more depth than the higher terpenes mainly because of the large fragrance industry that developed from the availability of sulfate turpentine from the paper industry. α‐ and β‐Pinene, the predominant terpenes found in turpentine, are used to manufacture other hydrocarbons such as myrcene, dihydromyrcene, alloocimene, camphene,p‐menthadienes, andp‐cymene. These hydrocarbons are used in turn as raw materials for producing products such as pine oil, nerol and geraniol, citronellol, linalool, menthol, campholenic aldehyde, citral, ionones and methyl ionones, camphor, citronellal, and hydroxycitronellal.

Methods employing petrochemical‐based raw materials such as acetone, acetylene, isobutylene, and isoprene have become very important commercial processes. Intermediates such as linalool, geranyl acetone, and citral for synthesis of Vitamins A and E are produced in large scale. The processes also yield linalool, citronellol, citronellal, and citral for fragrance uses as well as for intermediates for synthesis of many other aroma products.

Sesquiterpenes derived from natural sources are used as such for fragrance materials and for synthesis of other products. Sesquiterpenes covered include caryophyllene, longifolene, cedrene and cedrol, nerolidol and farnesol, α‐bisabolol, α‐santalol, valencene, nootkatene and nootkatone, patchouli alcohol, and guaiol and bulnesol.

Diterpenes such as gibberellic acid, phytol and isophytol, and taxol are discussed as are the triterpenes, lanosterol and squalene. The commercial aspects of the important group of tetraterpenes, the carotenoids, are also covered.
Fluorine‐Containing Polymers, Tetrafluoroethylene‐Ethylene Copolymers
Authors: Gangal Subhash V.
Published: July 2004

Perfluoroalkoxy (PFA) fluorocarbon resins are designed to meet industrial needs in chemical, electrical, and mechanical applications. These melt‐processible copolymers contain a fluorocarbon backbone in the main chain and randomly distributed perfluorinated ether side chains. A combination of excellent chemical and mechanical properties at elevated temperatures results in reliable high performance to the chemical processing and related industries. Chemical inertness, heat resistance, toughness and flexibility, stress‐crack resistance, excellent flex life, antistick characteristics, little moisture absorption, nonflammability, and exceptional dielectric properties are some of the key characteristics of these polymers.

Tetrafluoroethylene and perfluorovinyl ether are copolymerized in aqueous and nonaqueous media. The polymer is separated and converted into various forms, such as extruded cubes, powders, beads, or dispersions. Molecular weight and molecular weight distribution are controlled by a chain‐transfer agent. Sometimes a second phase is added to the polymerization reaction medium to improve the distribution of the vinyl ether in the polymer.
Fluorine‐Containing Polymers, Tetrafluoroethylene‐Perfluorovinyl Ether Copolymers
Authors: Gangal Subhash V.
Published: July 2004

Copolymers of ethylene and tetrafluoroethylene (ETFE) have been a laboratory curiosity for many years. These polymers exhibit a unique combination of mechanical, chemical, and electrical properties as well as excellent weatherability. However, thermal stress‐crack resistance is poor. The copolymer modified with a termonomer that undergoes free‐radical polymerization and does not cause undesirable chain transfer or termination during polymerization exhibits almost identical properties of the 1:1 alternating copolymer, but retains high ultimate elongation up to 200C. Thus, modified ETFE copolymers are the products of commercial value because they have good tensile strength, moderate stiffness, high flex life, as well as outstanding impact strength, abrasion resistance, and cut‐through resistance. Electrical properties include low dielectric constant, high dielectric strength, excellent resistivity, and low dissipation factor. Thermal and cryogenic performance and chemical resistance are good. These properties, combined with elasticity, make this material an ideal candidate for heat‐shrinkable film and tubing.

These polymers can be produced in aqueous, nonaqueous, or mixed medium with free‐radical initiators. The polymer is isolated and converted to extruded cubes, powders, and beads or dispersion.
Polyethers, Tetrahydrofuran and Oxetane Polymers
Authors: Pruckmayr Gerfried , Dreyfuss P. , Dreyfuss M. P.
Published: July 2004

This article reviews tetrahydrofuran and oxetane polymers and polymerization. The physical and chemical properties of polytetrahydrofurans and polyoxetanes are discussed, as well as the polymerization mechanism, including initiation, propagation, termination, chain transfer, kinetics, and copolymerization to give block, graft, and star copolymers. The most important commercial product is poly(tetramethylene ether) glycol (PTMEG), sold under the trade names Terathane (Du Pont), PolyTHF (BASF), and Polymeg (QO Chemicals). The manufacture of PTMEG is described in some detail, including the most recent industrial processes. Storage and handling of PTMEG, as well as specifications and standards of commercial products, are given. Test methods used in the 1990s are referenced, such as hydroxyl number, polymer molecular weight, and molecular weight distribution. Health and safety factors are discussed, as well as the economic aspects of PTMEG production. Most important uses of PTMEG are in elastomeric polyurethanes and polyesters. The same type of information is given for oxetane polymers, although no oxetane polymer has found any practical application and is thus not available commercially as of 1995.
Thallium and Thallium Compounds
Authors: Blumenthal Bob
Published: July 2004

Thallium and thallium compounds are produced by roasting zinc, copper, and lead ores. Demand and production of thallium and its compounds are small because of the element's high toxicity. Thallium(I) oxide, thallium(III) acetate, and thallium(III) nitrate are unstable. Other thallium(I) and thallium(III) compounds are stable. Certain alloys of thallium are used in bearings, contact points, as well as equipment for extreme conditions such as in polar regions or in space.
Composite Materials, Thermoset Polymer‐Matrix
Authors: Bauer Ronald S. , Stewart Steven L. , Stenzenberger Horst D.
Published: July 2004

Thermosetting unsaturated polyester resins are the most common fiber‐reinforced composite matrix today because of their low price, ease of use, and excellent mechanical and chemical resistance properties. Phenolic resins are used where the inherent flame retardance, high temperature resistance, or low cost overcome the processing difficulties and lower mechanical properties they possess. Other important thermosetting polymers used as composite‐matrix materials are epoxy resins and bismaleimides. This article discusses the manufacture, application, and properties of these resins and the composites made from them.
Thermography
Authors: Borrello Sebastian
Published: July 2004

Thermography is imaging by means of an infrared camera that detects thermal radiation emitted by all objects, converts the infrared radiation to electrical signals and generates a visible image. Recently developed mosaic infrared detector arrays make possible television displays with scene‐temperature sensitivity better than 0.10°C and resolution approaching CCD video cameras. Thermographic cameras that do not require cooled focal planes are becoming the sensors of choice for commercial and private use. Cooled systems having very high sensitivity continue to be developed for military applications. Thermal imaging applications include nighttime surveillance for law enforcement, industrial security, medical diagnostics and rescue operations. Commercial uses are imaging thermal anomalies to find material defects, thermal processing functions and overheating. The combination of thermography with spectral discrimination to achieve spectral imaging is under development for industrial process control and identification of toxic gases such as CO, NOx, SOxand ozone. This article includes a mathematical model for thermal imaging sensitivity and spectral discrimination sensitivity.
Chromogenic Materials, Thermochromic
Authors: Samat A. , Guglielmetti R.
Published: July 2004

Thermochromism is a reversible change in spectral and physico‐chemical properties as a result of heating and cooling.

Usually the response lies in the visible region. It is observed in complexed metals, in both organic and inorganic materials generally, and in all phases of matter, although predominately in solids and solutions for which the transition temperature is important for applications under heating or cooling.

The main examples given here are selected through metal complexes involving Co2+, Cu2+, or Ni2+with different ligands or anions, metal oxides such as VO2, Fe3O4and metal sulfides, organic and polymer compounds involving spiroheterocyclic systems, Schiff bases and related nitrogen‐containing compounds, bianthrones, and overcrowded ethenes. The breadth of the subject is very large taking into account the bibliography issued from different sources: inorganic and organic chemistry and physical investigations of the systems often associated with supports like polymer binders.
Thermoplastic Elastomers
Authors: Holden Geoffrey
Published: July 2004

Thermoplastic elastomers have many of the physical properties of vulcanized rubbers but can be processed as thermoplastics. This unique behavior has opened a new field of polymer science and technology. Since their commercial introduction in the 1960s, thermoplastic elastomers have become a significant part of the polymer industry. They are used in applications as diverse as adhesives, footwear, medical devices, automobile parts, and asphalt modification. Many of them are block copolymers with alternating hard and soft segments. The thermoplastic elastomers with polystyrene hard segments are the larget group and probably the most versatile; they can be produced over a wide range of hardness values and applied either in the molten state or from solution. Other examples are block copolymers with elastomers, either vulcanized or unvulcanized, in which the two components are intimately mixed together, but in most cases still remain as separate phases. Thermoplastic elastomers of this type are generally used as replacements for vulcanized rubbers. This article reviews the synthesis, morphology, structure–property relationships, and commercial applications of thermoplastic elastomers of all types.
Thermodynamics
Authors: Van Ness Hendrick C. , Abbott Michael M.
Published: July 2004

The first and second laws of thermodynamics are stated and applied to heat engines and refrigerators. Because chemical technology is concerned primarily with the processing of fluids, the dependence of volume on temperature and pressure and the phase behavior of gases and liquids are reviewed. The enthalpy, Helmholtz energy, and Gibbs energy are introduced, and the fundamental property relations that express these properties and the internal energy as functions of their special variables are developed. The energy balance for steady‐flow processes is presented, as are equations applying to the vapor–liquid phase transition. The property relations for ideal‐gas mixtures are developed, leading to the introduction of the fugacity, the fugacity coefficient, and residual properties, and their applications. Similar development of property relations for ideal solutions leads to the definition of excess properties. The criteria for phase equilibria and their application to vapor–liquid and other kinds of phase equilibria are considered. Finally, chemical‐reaction stoichiometry and the standard property changes of reaction are applied to chemical‐reaction equilibria.
Composite Materials, Thermoplastic Polymer‐Matrix
Authors: Wolf Clarence J.
Published: July 2004

The methods used to synthesize thermoplastic resins for use as the organic matrix for resin‐based thermoplastic composites are described. The synergism between the processing method chosen to prepare the composite and the synthesis route used to prepare the resin is emphasized. The synthesis and basic chemistry of commodity‐type resins, such as polyamides, polyolefins, polycarbonates, polyacrylates, and acetals, used in composites are discussed. In addition, the chemistry of advanced resin systems, such as polyether ketones, polysulfones, polysulfides, and polyimides, used in high performance composite systems also are presented. Both true thermoplastic resins and pseudothermoplastic resins, that is, resins that undergo some reaction during procesing, are discussed. Several new and potentially important methods for preparing thermoplastic resins for use in composites are highlighted.
Thiamine (B1)
Authors: Burdick David
Published: July 2004

Thiamine, usually meaning the hydrochloride, is a water‐soluble salt which as its pyrophosphate ester, plays essential roles in nearly all life forms as a cofactor for metabolic dehydrogenase and transketolase enzymes. Its biosynthesis in microorganisms and plants is tightly limited to very low levels by feedback and repression mechanisms. Animals are dependent on a regular supply in their diets to prevent deficiencies which can progress from mild subjective symptoms of malaise to serious degenerative disorders and death.

Knowledge of the biosynthesis of thiamine is limited and manufacture from biosources is not practical. All world production of thiamine is by chemical synthesis. All three of the major manufacturing groups use variants of one synthesis wherein the thiazole group is built up on the pyrimidine ring. The common intermediate, known asGrewe diamine, is synthesized from malononitrile or acrylonitrile, formate synthons, and acetonitrile. The thiazole ring is derived from carbon disulfide, butyrolactone, and acetate esters by the common intermediate thiolthiamine, which is oxidized to thiamine sulfate and then converted to other salts. Thiamine is sold as the hydrochloride and mononitrate salts which are widely used in foods, feeds, and multivitamin supplements. Thiamine is safe and stable when dry or in acidic solution, but degrades with base, irradiation, and nucleophilic attack.

Essentials of the history, occurrence, biosynthesis, biochemical and physiological functions, chemical transformations, manufacturing chemistry, analytical methods, safety and handling, product forms, derivatives, analogues, and uses of thiamine are discussed.
Magnetic Materials Thin Films and Particles
Authors: Wernick Jack
Published: July 2004

High density recording materials for audio and video systems are comprised of magnetic materials in the form of thin films and particles. The magnetic properties of these systems are discussed. Materials systems used for tapes and disks include those based on iron oxide, chromium dioxide, ferrites, and iron‐ and cobalt‐based alloys. Metallic, ie, alloy‐based media are usually in the form of thin films, typically sputtered films having protective overcoats. Magnetic thin‐film deposition techniques are presented.

The development of magnetooptical thin‐film material systems is of interest because of the need for greater capacity for the storage of digital information. Ferrimagnetic ternary amorphous alloys containing rare‐earth elements, as well as cobalt–platinum multilayers, are employed. Future developments are expected to focus on antiferromagnetically coupled superlattices exhibiting giant magnetoresistance. These magnetic superlattices are described.
Thiophene and Thiophene Derivatives
Authors: Fuller Lance S.
Published: July 2004

Industrial demand for thiophene and its derivatives has escalated since 1980. Applications in the electronic field will take it into the twenty‐first century, whereas pharmaceutical, agrochemical, and dyestuff requirements continue to account for existing demands. Synthesis of the parent ring system, along with simple alkyl derivatives, has changed little over the years. An outline of the vapor‐phase route, the best practical environmental option to produce these materials, is given. Ring synthesis of specific derivatives has been developed into commercial‐scale operations from chemistry identified in the late 1950s and early 1960s, following market interest in such products as dyestuff, agrochemical, and pharmaceutical intermediates. Reactions of the thiophene have been noted, along with useful spectroscopic and physical chemistry data as well as additional toxicity and ecotoxicity data for thiophene derivatives. Biotic degradation of thiophene is minimal, and halothiophenes, in particular, are environmentally hazardous in aqueous systems.
Thioglycolic Acid
Authors: Labat Y.
Published: July 2004

Thioglycolic acid and its derivatives as well as various other mercaptocarboxylic acids have become widespread. Both the mercapto and carboxylic functions in thioglycolic acid are chemically active, as is the methylene group in esters under alkaline conditions. The most important reactions involve the thio disulfide interchange reactions with cystine units in hair protein, keratin, which property is applied in cosmetology for hair waving, and the formation of esters to give tin stabilizers for poly(vinyl chloride). For esters, the ability to build N and S heterocycles promises prospective development in fine chemistry. Other mercaptocarboxylic acids have experienced interesting developments, mainly as polymer modifiers and polymer stabilizers.

Thioglycolic acid is manufactured from the inexpensive starting materials chloroacetic acid and alkali sulfhydrates. Thioglycolic acid is degraded by self‐esterification but is stable at low temperatures. All processes which produce thioglycolic acid are characterized by salt formation.
Thiols
Authors: Roberts John S.
Published: July 2004

The chemistry of thiols is a diverse area. Many thiols are of economic importance, with applications such as rubber intermediates, cosmetics additives, herbicides, gas odorants, and lube additive intermediates. Thiols are characterized by their strong odor. The preparations and reactions of thiols, as well as their use as intermediates in the production of commercial products, are discussed.
Thorium and Thorium Compounds
Authors: Clark David L. , Keogh D. Ww , Neu Mary P. , Runde Wolfgang
Published: July 2004

Thorium, a naturally occurring radioisotope, and thorium compounds, primarily where thorium is present in the+4oxidation state, are discussed. The main interest in thorium is as a nuclear fuel, but thorium and its compounds have many specialty uses, for instance, as gas, lantern mantels, and catalysts. Thorium has a rich coordination and organometallic chemistry. A drawback to using thorium in many processes is the chemical reactivity of the metal as well as the inherent radioactivity of all thorium isotopes. Health and safety factors essential for working with thorium are discussed.
Titanium and Titanium Alloys
Authors: Froes F. H. (Sam)
Published: July 2004

Titanium, the ninth most abundant element, is used principally as an oxide in paint filler for its high refractory index and as a metal in aerospace and industrial applications for its high strength‐to‐density ratio and excellent corrosion resistance. This article covers the locations and reserves of principal ore bodies and their conversion by sulfate or chloride refining processes to high purity oxides for the pigment industry, and the conversion of the intermediate chloride by magnesium or sodium reduction to metallic sponge for the metal industry.

The principal metal melting processes to produce ingots from sponge are reviewed, along with the metalworking processes for converting ingots to mill products. The influence of alloying elements on properties and microstructure is discussed, along with the mechanical properties and characteristics of the principal alloys used in aerospace and industrial applications. Methods and procedures related to the fabrication of metal components into useful application components are covered. The primary uses of both the oxide and the metal are summarized, along with the economics associated with the production of the metal and oxide.
Toluene
Authors: Ozokwelu E. Dickson
Published: July 2004

Changes in the environment necessitate that information on commodity chemicals like toluene be updated periodically. Because of the global technological and economic changes that have occurred since 1983, considerable material on improved and emerging technologies for the manufacture of toluene and also on the economic aspects and uses of toluene are included.

Physical and chemical properties are presented. Manufacture and processing aspects treated include production of toluene along with benzene and xylenes from reformate and highlight the improvements on toluene–benzene recovery by extraction and extractive distillation. Lastly, emerging technologies for the manufacture of BTX from light hydrocarbons are reviewed. Toluene supply and demand are discussed. The declining effect of the introduction of Reformulated Gasoline in Fall 1994 on the use of toluene for gasoline blending and the increase in demand of toluene for use in disproportionation plants to produce xylenes are analyzed. Specifications, standards, and quality control are outlined. The analytical and test methods and storage procedures are listed, and health and safety factors (toxicology) are discussed. Uses and derivatives are presented.
Toxicology
Authors: Ballantyne Bryan , Fong William George
Published: July 2004

Toxicology is the study of interactions between chemicals and biological systems to determine quantitatively the potential for to produce injury resulting in adverse health effects. The relationship of exposure dose and the nature and magnitude of any effect, ie, dose‐response relationship information, is valuable in determining causal relation and relevance of exposure conditions, so as to allow estimates of hazard. Toxicological investigations attempt to define the nature of the harmful effect; severity of effect as a function of exposure dose; mechanism causing the effects; detection, recognition, and quantitation of toxic effects; and reversibility of toxic injury.

Toxic effects may be classified as local or systemic; and as latent, persistent, cumulative, or transient. They include inflammation, necrosis, immunosuppression, neoplasia, mutagenesis, enzyme inhibition, teratogenesis, and others. Factors influencing toxicity include number, magnitude, and routes of exposures; and time of dosing, as well as formulation and impurities of materials. Routes of exposure include swallowing, through the skin, inhalation, and through the eye, and may also be multiple. The discrepancy of amount of a material passing to the liver related to route of exposure may influence the degree of toxicity, as may the residence time of materials and their metabolites in an organism before excretion and their capacity for storage.

Dose–response relationships are useful in determining causality, range of sensitivity in a population and hence of hazard, assessment of no‐ or minimum‐effects doses, and comparisons of materials and species.

Toxicology testing procedures may be general or specific, and many guidelines must be followed. General studies monitor body weight, hematology, chemical pathology, and organ weight, among others, and types of studies include acute toxicity studies, short‐term repeated studies, and chronic and subchronic toxicity studies. Examples of specific studies include primary irritancy and immune‐mediated hypersensitivity studies, and neurological and behavior toxicology. Review of studies and the relevance of toxicology in hazard evaluation are briefly examined.
Chlorocarbons and Chlorohydrocarbons, Toxic Aromatics
Authors: Safe Stephen H.
Published: July 2004

Halogenated hydrocarbons such as the polychlorinated biphenyls (PCBs), hydroxy‐PCBs, polybrominated diphenyl ethers (PBDEs), polychlorinated naphthalenes (PCNs), and chlorinated insecticides (lindane) have been widely used industrial compounds. These chemicals are lipophilic and their release into the environment results in bioaccumulation in adipose tissue and persistence due to their chemical stability and resistance to metabolic breakdown. Thus, the more widely used PCBs and lindane have been identified in almost every component of the global ecosystem including fish, wildlife, and humans. Risk and hazard assessment of the highly complex halogenated hydrocarbon mixtures is difficult; however, at least one subgroup of chemicals within these mixtures can be evaluated. Several PCB congeners exhibit aryl hydrocarbon receptor (AhR) agonist activities and their potencies relative to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) have been determined and used to calculate TCDD or toxic equivalents (TEQs) for various mixtures. However, risk assessment of most other halogenated hydrocarbons is not well defined and requires further research to determine their activities and relative potencies.
Trace and Residue Analysis
Authors: Ahuja Satinder
Published: July 2004

It is generally recognized that trace analysis implies those analyses that are carried out around 0.0001% or ppm level. Ultratrace analysis, ie, beyond what is ordinarily called trace analysis, can be then defined as analysis performed below ppm or µg/g level. Residue analysis relates to the analysis of residual materials left from an operation, eg, solvents left in pharmaceutical products or pesticides left in food. Analyses performed at or below ppm level are described. Sampling, sample preparation, sample cleanup, and method validation are discussed. In addition, a number of methodologies are covered, such as atomic absorption/emission spectrometry, neutron activation analysis, tlc, gc, hplc, hyphenated methods such as gc/ms and lc/ms, capillary electrophoresis, supercritical fluid chromatography, and immunoassays that allow analyses of both organic and inorganic samples. Applications include areas such as environment, explosives, food, pharmaceuticals, biotechnology, and a number of miscellaneous fields.
Transportation
Authors: Hoffman Stanley , Moreno Jeffrey O. , Booth Karyn A. , Cobb Antoine P. , Fortin Richard D.
Published: July 2004

A wide range of issues and matters relevant to the transport of chemicals is addressed. In particular, the various modes of transport, including railroad, motor carrier, water carrier, pipelines, and air transport, and the role played by each in the transport of chemicals is discussed. In addition, the significance of regularly used shipping terms and documents are explained. The different laws applicable to interstate and intrastate transportation, and how to identify under which jurisdiction a particular shipment will be regulated, also are addressed. Changes in the economic regulation of the various modes of transport are explained and the significance of those changes to chemicals shippers is explored. Economic regulation includes important distinctions between contract, common, and private carriage, and the allocation of responsibility between shippers and carriers for freight loss and damage. Finally, safety and hazardous materials transport regulations, a critical concern for chemical shippers and carriers alike, are discussed.
Triphenylmethane and Related Dyes
Authors: Thetford Dean
Published: July 2004

A brief introduction describing the structure and dyeing properties, eg, lightfastness and color, of the triphenylmethane dyes is given. The dyes are also classified in terms of their application class, giving their historical and present‐day usage in textiles and paper. Further details on the relationship of the structure and the various substituents on the reactivity, spectral characteristics, and fastness properties are discussed.

The significant industrial processes for the manufacture of triphenylmethane dyes are outlined through examples of the synthesis of the more important dyes like malachite green, methyl violet, and crystal violet. New reagents and kinds of chemical technology are described where these have been used to improve the older processes and alleviate environmental problems. The toxicology associated with the triphenylmethane dyes is also mentioned in relation to their use as food colorants or dyes, and the environmental concerns of effluent treatment is briefly mentioned.

Production statistics for triphenylmethane dyes in the United States are given for the period between 1975 and 1995, with suitable references also provided giving world figures. The many different areas in which these dyes are employed are described, along with more recent high technology uses.
Tungsten Compounds
Authors: Penrice Thomas W.
Published: July 2004

Tungsten combines with many other elements to form simple stable compounds. It readily polymerizes but the chemistry of aqueous solutions is very complex. This is exemplified by the large number of polytungstates. The chemical uses of tungsten have increased substantially in more recent years.

The hexacarbonyl has potential as a lubricant additive and as a dye and pigment. The halides are useful as starting materials in the chemical vapor deposition of tungsten. The oxides are important intermediate products in the stepwise reduction in hydrogen to the metal. Tungsten bronzes constitute a series of well‐defined nonstoichiometric compounds. The sodium tungsten bronzes are interesting not only for their intense color range but exhibit both positive and negative coefficient of resistance as the sodium:tungsten ratio changes. Sodium tungsten bronzes help the catalytic oxidation of carbon monoxide and reformer gas in fuel cells.

The tungstates are an important class of materials. The metatungstates are important starting materials for production of tungsten catalysts because of the high solubility in water. Ammonium paratungstate is the intermediate material of choice between chemical recovery from ores and the reduction to tungsten metal. The interstitial compounds, particularly with carbon, represent the largest application for tungsten in cemented carbides. Tungsten compounds, especially the oxides, sulphides, and heteropoly complexes, form stable catalysts for a variety of chemical processes in the petroleum industry and in chemical synthesis. Other uses include fireproofing of textiles, as additives in lubricants and antifreeze solutions, in inks and dyes, as phosphors in fluorescent lights, and for improvement of conductivity of tin oxide coatings on aircraft windows. Because soluble tungsten compounds show varying degrees of toxicity, exposures in the workplace are regulated.
Urethane Polymers
Authors: Ulrich Henri
Published: July 2004

The properties of thermoplastic and thermoset polyurethanes are discussed. The subjects include flexible and rigid polyurethane foams, poly(urethane isocyanurate) foams, thermoplastic polyurethane elastomers, thermoset cast and RIM elastomers, engineering thermoplastics, liquid crystalline polyurethanes, and polyurethane containing interpenetrating polymer networks. Principal raw materials, such as isocyanates, polyether polyols, and polyester polyols, as well as catalysts, fire retardants, and surfactants, are described. The manufacture of flexible foam, rigid foam, coatings, adhesives, sealants, and elastomers are included, as is the use of polyurethane ionomers in aqueous dispersions and blocked isocyanates in one‐component and powder coatings applications. The global trend in polyurethanes is a shift from toluene diisocyanate‐based formulations to polymeric isocyanate and 4,4′‐methylenebis(phenyl isocyanate) whenever possible, and substitution of chlorinated fluorocarbon blowing agents by hydrochlorofluorocarbons, hydrofluorocarbons, or hydrocarbons. Recycling of polyurethanes, health and safety factors, including toxicity and safe handling of isocyanates and tertiary amine catalysts, as well as principal uses of polyurethanes and market information, are all discussed.
Vaccine Technology
Authors: Hsieh Chia‐Lung , Ritchey Mary B.
Published: July 2004

A vaccine is a preparation used to prevent a specific infectious disease by inducing immunity in the host against the pathogenic microorganism. The practice is also called immunization. Beginning in the 1950s, with the discovery of antibiotics, interest in vaccine research faded; however, the development of biotechnology and modern immunology has created new opportunities for producing new antigens and vaccine research has become a significant focus once again. Vaccines have been developed against poliomyelitis, diphtheria, tetanus, pertussis, measles, mumps, rubella,Haemophilus influenzaserotype b, hepatitis B, and varicella are all in commercial use. Vaccines being developed include those against meningitis, rotavirus, respiratory syncytial virus, parainfluenze, otitis media, herpes simplex, influenza, malaria, gonorrhea, and the human immunodeficiency virus. All are discussed, as well as future technology, the effects of genetic engineering, adjuvants, and economic aspects.
Vanadium Compounds
Authors: Woolery Mike
Published: July 2004

Vanadium is widely dispersed in the earth crust. Primary industrial compounds produced directly from vanadium raw materials are principally fused pentoxide, air‐dried pentoxide, and technical‐grade ammonium metavanadate. Recovery of vanadium from dolomitic shale by salt roasting, acid leaching, and amine solvent extraction is common. Conversion of fused pentoxide to alloy additives is by far the largest use of vanadium compounds. Air‐dried pentoxide, ammonium vanadate, and some fused pentoxide are used as such, purified, or converted to other forms for catalytic, chemical, ceramic, or specialty applications. Physical and chemical properties, manufacturing, health and safety factors, and economic aspects are discussed.
Fibers, Vegetable
Authors: Young Raymond A.
Published: July 2004

Plant‐derived vegetable fibers are classified according to their source in plants as bast, leaf, or seed‐hair. The fibers in bast and leaf plants are integral to the plant structure, providing strength and support. The principal chemical component of vegetable fibers is cellulose, with varying amounts of lignin and hemicelluloses also usually present; thus the fibers are also referred to as cellulosic or lignocellulosic. Vegetable fibers are usually stiffer but less tough than synthetic fibers. The fibers are grown throughout the world but mostly in tropical and subtropical climates in developing countries. The principal bast fibers are flax, jute, and hemp which are utilized primarily for fabrics (linen‐flax, hessian‐jute), bags, ropes, in newer biobased composites and as a source of papermaking fibers, principally cigarette papers. The primary leaf fibers are abaca and sisal, which have uses similar to bast fibers, except fabrics are not produced from the leaf fibers. Cotton, coir, and kapok are the principal seed‐hair fibers, with cotton by far the most important commercial vegetable fiber. Bast fibers are obtained from the plant, after harvest, by water retting (rotting) in ponds or streams. The leaf fibers are obtained by crushing and scraping followed by washing. Vegetable fibers are generally graded according to color, luster, cleanliness, strength, fineness, and uniformity. The world market for vegetable fibers has dropped dramatically in recent years because of periods of economic recession and synthetic fiber replacements.
Vinegar
Authors: Webb A. Dinsmoor
Published: July 2004

Vinegar is a dilute (4–10%) water solution of acetic acid plus other organic and mineral constituents which vary greatly with the source material from which the vinegar comes.Acetobactercatalyzes oxidation of ethanol to acetic acid. Ethanol comes fromSaccharomycesfermentation of sugary plant materials and from solutions of hydrolyzed starch. Ethanol also is synthesized from petroleum or other basic raw materials.

Prehistoric vinegars likely came from ambient microorganisms contacting sugary solutions such as diluted honey. Pasteur found in the mid‐nineteenth century that microorganisms were responsible for both alcoholic and acetous conversions, and modern technology has made possible the wide range of vinegars available today. Traditional Balsamic and Orleans types, with their complex and estery odors, are appreciated for table use, as are the simpler, less costly types produced by generator and submerged culture techniques. Many of these depend upon added herbs and spices for complexing the simple acid taste. For industrial and pickling purposes, very highly concentrated vinegars are available.

Techniques of vinegar production parallel those used in processing other clear liquid foods. Crushing, pressing, fermenting, heating, cooling, centrifuging, filtering, clarifying, stabilizing, blending, pasteurizing, and filling into bottles are the principal steps involved. Since vinegars are quite acid, contacting equipment must be stainless steel, plastic, glass, or wood.
Vinyl Acetate Polymers
Authors: Cordeiro Cajetan F.
Published: July 2004

This article provides information related to the chemistry, manufacture, and use of poly(vinyl acetate). Summary information is provided on vinyl acetate as the primary ingredient in the manufacture of the polymer. This information focuses on the chemical and physical properties of the material and the handling and safety aspects pertinent to its use in a polymerization system. The key material properties of poly(vinyl acetate) homopolymer and copolymers are described. The influences of key components of the polymerization recipe are discussed, such as the effect of the stabilizers, comonomers, and chain‐transfer agents on the reaction and product. Polymerization process aspects are covered with a focus on emulsion polymerization. The mechanisms involved in the vinyl acetate polymerization reaction are discussed. An overview is provided of the applications of the homopolymer and copolymers in adhesives, paint, paper, and other areas. General information is provided in these areas with references which can be used to obtain more specific information.
Vinyl Acetal Polymers
Authors: Knapczyk Jerome W.
Published: July 2004

Poly(vinyl acetal) resins are made by the acid‐catalyzed acetalization of poly(vinyl alcohol) with aldehydes. The reaction favors formation of the 1,3‐dioxane ring, which is a characteristic feature of this class of resins. As of this writing (ca 1997), only poly(vinyl butyral) and poly(vinyl formal) are made in sizable commercial quantities. Most poly(vinyl butyral) is plasticized and made into interlayer for vehicle and architectural safety glazing. The primary use for poly(vinyl formal) is as an important component in coatings for electrical wire and cable insulation. Applications for poly(vinyl butyral) and poly(vinyl formal) resins make use of their toughness, resilience, optical clarity, high pigment/filler binding capacity, and the high adhesion the resins may provide when appropriately formulated.

The history and general characteristics of poly(vinyl acetal) resins are briefly reviewed. Chemical and physical characteristics, manufacture, and principal applications are discussed. Special attention is given to poly(vinyl butyral) and its use for safety glazing interlayer, because glazing interlayer is by far the largest single application for the poly(vinyl acetal) class of resins.