bluuebunny/crossref_metadata_2025 huggingface dataset:
Pyrazoles, Pyrazolines, and Pyrazolones
Authors: Kornis Gabe I.
Published: July 2004

The title compounds are five‐membered heterocycles having two adjacent nitrogen atoms within the ring. Pyrazoles have two endocyclic bonds and possess aromatic and tautomeric properties. Pyrazolones also have two double bonds, one of which is attached to an exocyclic oxygen atom. Pyrazolines have only one endocyclic double bond. The structural elucidation of pyrazoles and derivatives has been greatly aided by nuclear magnetic resonance spectroscopy, especially for distinguishing between isomeric structures. Pyrazoles are stable compounds and their boiling points increase with an increase in the number of alkyl groups on carbon; solubility in organic solvents is also increased. Substitution on nitrogen decreases the boiling point because of the elimination of hydrogen bonding. Pyrazolines are usually liquids having high boiling points and low water solubility, and are basic in nature. Pyrazolones are often crystalline solids and their characteristics are strongly influenced by the predominant tautomeric form. Pyrazoles can react with both acids and bases, and can be halogenated, nitrated, and acylated on both N and C. Pyrazolines are much less stable, resulting in facile ring opening. Pyrazolones react with diazonium salts, an important process in the dye industry. The preferred synthetic method for the title compounds utilizes the reaction of hydrazines with bifunctional compounds, such as β‐diketones and esters, and β‐keto acetylenic compounds. In an alternative procedure, diazo compounds replace hydrazines and ring formation takes place via 1,3‐dipolar cycloaddition. Pyrazoles and pyrazolones are widely used in the pharmaceutical industry to alleviate inflammation, fever, pain, and infections. To a lesser extent, they are also used as insecticides and herbicides. Pyrazolones linked to azo compounds are extensively used in the dye industry; some pyrazolines display insecticidal activity.
Pyridoxine (B6)
Authors: Burdick David
Published: July 2004

Vitamins (Pyridoxine–B6). Burdick, David (Hoffmann‐La Roche Inc.). Vitamin B6consists of a group of six biochemically interconvertible substances, pyridoxine, pyridoxol, pyridoxamine, and their 5′‐phosphates. These are found in the tissues and fluids of virtually all living organisms. Pyridoxal phosphate plays essential roles in over 100 enzymes involved with amino acid biochemistry. Humans and animals cannot biosynthesize vitamin B6and require it in their diets or in supplements to prevent a number of metabolic and neural disorders. Humans require 2 mg/d in their diets. Chemical interactions with some food and drug components can reduce bioavailability of vitamin B6.

Pyridoxine is the most stable of the B6vitamers. It is quite stable when dry or in acidic solution but degrades with base or irradiation. Production from natural sources or bioprocesses is not practical. All of the more than 3000 t/yr world production is made by chemical synthesis by variants of a cycloaddition route of substituted oxazoles with butenediol derivatives. Pyridoxine hydrochloride is widely used in foods, feeds, and multivitamin supplements.

Essentials of the history, occurrence, biosynthesis, biochemical and physiological functions, chemical transformations, manufacturing chemistry, analytical methods, safety and handling, product forms, and uses of vitamin B6are briefly reviewed.
Pyridine and Pyridine Derivatives
Authors: Scriven Eric F. V. , Toomey Joseph E. , Murugan Ramiah
Published: July 2004

Scriven, Eric F. V., Toomey, Joseph E., Jr., and Murugan, Ramiah (Reilly Industries, Inc.). Commercial manufacture, industrial chemistry, and market uses of pyridine and pyridine compounds are reviewed. Pyridines often serve as intermediates for manufacture of products that are bioactive, such as medicinals, herbicides, insecticides, and fungicides. Significant end products for these market applications are identified. Important physical properties are also listed. Discussion of manufacture includes raw materials used, energy utilization, economics, toxicity of compounds, and safety factors. Vol. 20, pp. 641–679, 110 refs. to September 1994.
Pyrrole and Pyrrole Derivatives
Authors: Anderson Lowell Rr , Liu Kou‐Chang
Published: July 2004

Pyrrole is a planar, aromatic, five‐membered heterocycle which provides the fundamental structural subunit for many of the most important biological molecules, such as heme and chlorophyll. Extensive delocalization of the lone pair of nitrogen electrons throughout the system accounts for the lack of basicity and pronounced aromatic character of pyrrole systems.

Pyrrole derivatives are often prepared by condensation of amines with carbonyl‐containing compounds. Several widely used synthetic reactions that are variations of this procedure are discussed. These include the reaction of an α‐aminoketone with β‐dicarbonyls (Knorr), the condensation of an α‐haloketone with a β‐ketoester in the presence of an amine (Hantzsch), and the condensation of a 1,4‐diketone with ammonia or a primary amine (Paal‐Knorr).

Brief descriptions of the preparation and utility of some of the very large number of pyrrole derivatives are provided. These include the hydroxypyrroles, as well as aldehydes, ketones, acids, esters, and various reduced forms, such as pyrrolines and pyrrolidines. Condensed pyrroles with two, three, or four pyrrole nuclei are well known, as are the larger polypyrroles. Polypyrroles form highly stable, flexible films which are electrically conducting.

Pyrrolidinones are five‐membered nonaromatic cyclic amide systems prepared by the reaction of butyrolactone with ammonia or a primary amine at relatively high temperatures. Several are commercially available and are widely used as intermediates, wetting agents, and solvents with relatively low toxicity. The important monomer 1‐vinyl‐2‐pyrrolidinone is derived from 2‐pyrrolidinone.
Quality Control
Authors: Silverstein Irwin
Published: July 2004

Quality in the chemical industry has come to encompass three areas: quality control, quality assurance, and quality systems. The importance of quality to the chemical industry is in its use as a competitive tool in international trade. Historically, industrial quality issues in the twentieth century were emphasized in Japan to reduce costs and improve product quality. Quality improvement activities can often lead to a large corporate economic gain.

Quality control responsibilities involve issues such as sampling plans, calibration, and replicate analyses. Statistical quality control and laboratory information management systems are often employed. Quality assurance, which encompasses quality control, covers such activities as employee training, quality system documentation, preparation and transfer of test methods, and applying the tools of quality, quality audit, and customer complaints.

Different systems are compared. The product quality system Good Manufacturing Practices, the quality system ISO 9000 standard, and the quality performance recognition of the Malcolm Baldridge National Quality Award are discussed.
Radiopharmaceuticals
Authors: Lazewatsky Joel L. , Crane Paul D. , Edwards D. Scott
Published: July 2004

Radiopharmaceuticals are radioactive drugs used as imaging and therapeutic agents in nuclear medicine. Commonly performed clinical studies are discussed and the approved radiopharmaceuticals are presented in terms of biological distribution, disease targets, and chemical and physical properties. Advantages and disadvantages of nuclear medicine techniques are presented.

The second section comprises a discussion of isotopes used in both diagnostic and therapeutic nuclear medicine. Specific properties as well as usage and means of production are given. The chemistry of radiopharmaceuticals including synthesis, labeling, and analysis is presented followed by discussion of the instrumentation used for both
in vivo
and sample measurement of radioactivity. Measurements of dispensed doses are described as are imaging systems and instruments for radiation safety. Radiopharmaceutical safety issues, including both radiation dosimetry and a brief discussion of chemical toxicity, are presented and formulation and packaging of materials is discussed. Anticipated developments and new directions for the industry are presented.
Radiation Curing
Authors: McGinniss Vincent D.
Published: July 2004

The interaction of electromagnetic radiation with organic substrates is of widespread interest and has broad commercial applications. The use of electromagnetic radiation to alter the physical and chemical nature of a material is sometimes termed radiation curing technology. In radiation curing, electromagnetic radiation interacts with organic substrates to develop cross‐linked or solvent‐insoluble network structures. For example, a preformed thermoplastic polymer that interacts directly with certain types of ionizing (high energy) radiation from a given source of energy can develop into cross‐linked or network structures having higher melting points, improved heat resistance, and better chemical resistance than the original thermoplastic polymer starting materials. Similar types of high energy radiation can be used to cross‐link (cure) organic coatings, provided that the liquid coating composition contains reactive vinyl‐unsaturated components such as allyl, acrylate, methacrylate, styrene, and fumarate reactive groups.

Radiation curing technology involves consideration of at least four main variables: type of radiation source; organic substrate to be irradiated; kinetics and mechanisms of radiation energy–organic substrate interactions; and the final chemical, physical, and mechanical properties associated with the formation of three‐dimensional (cured) network structures. The conversion of electrical energy into infrared, ultraviolet, and high energy electromagnetic radiation has gained worldwide acceptance as an efficient and economical method for modifying polymeric materials. These radiation‐modified polymer systems are associated with many different types of products produced under a wide diversity of manufacturing operations.
Reactor Technology
Authors: Tarmy Barry L.
Published: July 2004

Reactor technology presents an overview of the underlying principles of chemical reaction engineering and the practices used in their application. Central to the commentary are the varied nature of chemical reactors, operating conditions, external operating environments, developmental history, industrial application, and evolutionary changes in the context of feed supply and reactant requirements, production and product specifications, fixed and operating costs, process integration, safety concerns, and environmental considerations. The principal reactor types and their characteristics are presented along with selection, development, and design considerations, and descriptions of the complex flow behavior within reactors. Also covered are the changing roles of computer simulation of reactor performance, laboratory experimentation, pilot‐plant usage, and scale‐up methodology. Following these expositions is a survey of industrial reactor usage by reactor type, which features selected examples of batch and semibatch reactors, continuous‐flow stirred‐tank reactors, thermal tubular reactors, bubble columns, airlift reactors and spray columns, tubular fixed‐bed reactors, single‐ and multiphase fixed beds, and fluid‐bed and gas–liquid–solid fluidization reactors.
Petroleum Refinery Processes
Authors: Speight James
Published: July 2004

Petroleum refining or petroleum processing is the recovery and/or generation of usable or salable fractions and products from crude oil, either by distillation or by chemical reaction of the crude oil constituents under the effects of heat and pressure. Petroleum refining also involves treating the raw products by a variety of finishing processes to yield marketable products.

A refinery is an integrated group of manufacturing plants that vary in number according to the variety of products produced; it must be flexible and able to change operations as needed. Refinery processes must be selected to produce products according to demand.

This article deals with the processes used to refine petroleum, from the initial pretreating of the well fluids to the finishing processes for products as well as the gas treating processes for reducing emissions to the environment.
Fibers, Regenerated Cellulose
Authors: Woodings Calvin
Published: July 2004

Fibers manufactured from cellulose are either derivative or regenerated; historically they are designated man‐made fibers and distinguished from fibers based on synthetic organic polymers. A derivative fiber is one formed when a chemical derivative of a natural polymer, eg, cellulose, is prepared, dissolved, and extruded as a continuous filament, and the chemical nature of the derivative is retained after the fiber formation process. A regenerated fiber is one formed when a natural polymer, or its chemical derivative, is dissolved and extruded as a continuous filament, and the chemical nature of the natural polymer is either retained or regenerated after the fiber formation process. The difficulties of making solutions of natural cellulose from which fibers can be spun has led to most fabricated cellulosic fibers being regenerated from more readily soluble derivatives of cellulose. It is the technology of making these fibers that is the subject of this article.

Textile fibers and filaments composed of regenerated cellulose are called rayons. In Europe the fibers are now generally known as viscose; the term viscose rayon is used whenever confusion between the fiber and the cellulose xanthate solution (also called viscose) is possible. In addition to the viscose process, the cuprammonium rayon and direct dissolution processes are also covered. Fiber properties and environmental and commercial issues are discussed.
Reinforced Plastics
Authors: Bastone Andrew L. , Katz Steven G.
Published: July 2004

Reinforced plastics, also known as fiber glass‐reinforced plastics, glass‐reinforced plastics, fiber glass, and composites, are a relatively small (5%) but very important part of the total plastics market. Common to all reinforced plastics are resin and reinforcement. Resins can be thermoplastic or thermosetting. Reinforcements are usually fibers of glass or other materials, and can be configured in many ways, such as continuous or chopped strands, milled fibers, rovings, mats, and woven fabrics. Reinforced plastics may also include fillers, curing agents, colorants, and other additives that impart specific properties. The selection process for a given application requires simultaneous consideration of product design, constituent materials, production requirements, and required physical, mechanical, and chemical properties.

The commonly used manufacturing processes include hand lay‐up and spray‐up; vacuum bag, pressure bag, and autoclave molding; resin‐transfer and cold press molding; reaction injection molding; compression molding using bulk molding compound, sheet molding compound, wet systems, and reinforced thermoplastic sheet; injection molding; pultrusion; and filament winding. The successful use of reinforced plastics results from proper design, utilization of the benefits these materials offer, process selection, tooling cost advantages that fit the production needs, and consideration of life cycle economics.
Renewable Energy Resources
Authors: Torrero Edward A.
Published: July 2004

Only a small fraction of U.S. electricity needs are supplied by renewable energy technologies other than hydropower, because of their relatively high cost and the economics of the electric utility industry, which is faced with an increasingly competitive environment and is generally awash in surplus power. Despite the formidable technical hurdles that these technologies have overcome to bring costs down and increase reliability, further inroads have been thwarted by the lower cost of natural gas and the efficiency of gas‐fired generating plants.

As costs continue to decline, however, the renewable energy market can be expected to grow, particularly if possible global warming trends continue to be linked with greenhouse gases, such as those emitted by fossil fuels. Other factors that are increasing interest in renewable energy include niche cost advantages, regulatory pressures, customer service requirements, fuel flexibility, and security.

The extent to which each technology is poised to advance is described in progress reports on photovoltaics, solar‐thermal power, and wind, biomass, waste‐to‐energy, geothermal, hydropower, and wave energy.
Research/Technology Management
Authors: Miller J. A. , Norling P. M. , Collette J. W.
Published: July 2004

In a period of restructuring and change in the world, especially in the United States and in U.S. firms, technology leaders must be broadly versed in their firms' businesses and functions. These leaders must have the technical edge and be able to function with credibility in their companies as they deal with change, participate in setting direction, and take the necessary steps to ensure that the importance of technology is well understood and used. They must, furthermore, ensure that the necessary support for research is provided, that resources are adequate, that core competencies are preserved, and that their R&D organizations are productive and effective. This requires leaders who cannot only articulate the value of new technology, but who are courageous in the promotion of programs that may upset the normal equilibrium desired by the business.
Resins, Natural
Authors: Class Jay B.
Published: July 2004

Class, Jay B. (Hercules Incorporated). Natural resins are solid, amorphous, usually transparent or translucent organic substances that originate from plant secretions. They may be obtained directly as tree or plant exudates, collected by hand or below the ground, or mined from underground deposits. Shellac is refined from insect secretion which coats twigs of a host tree. The resins may be altered by methods of isolation, or modified in production to increase their industrial utility. In this article, the resins are discussed in five groups. Rosin and modified rosins are commercially the most important natural resins, with an annual production of almost a million tons. The isolation of rosin from pine gum, pine stumps, and tall oil is discussed, as well as properties, composition, chemical reactions, and derivatives. Principal uses are described, such as paper sizing, printing inks, and adhesives. The origin, properties, and uses of traditional natural resins are described, with special emphasis on resins that are available in the United States. These are Manila copal, pontianak, dammar, East India resins, gum elemi, sandarac, and mastic. Resins with limited availability, such as kauri, congo, accroides, and amber are also discussed. In a section on natural resins in medicines, flavors, and fragrances origin, composition, and uses are described for balm of Gilead, balsam of Peru, balsam of Tolu, copaiba, gum benzoin, guaiac, myrrh, olibanum (frankincense), and storax. Properties are described for the asphaltites, such as gilsonite, glance pitch, and grahamite, as well as for Utah coal resin. The history, cultivation, production, and composition of shellac are discussed. Uses in protective coatings, pharmaceuticals, candy and fruit coatings, and electrical applications are described.
Rhenium and Rhenium Compounds
Authors: Millensifer Tom A.
Published: July 2004

Rhenium is one of the least abundant elements, existing in nature only in trace quantities. The commercial source of rhenium is in molybdenite by‐product material from porphyry copper ores. Rhenium oxides are driven off upon roasting the molybdenite concentrate. Rhenium is separated, converted to an ammonium salt, and reduced to the metal.

The metal has found many high temperature uses, both as pure metal and as alloys with elements such as molybdenum, tungsten, and nickel. Uses include filaments in a wide array of bulbs and mass spectrometers, in thermocouples, and in heating elements. It is also used as a catalyst in the production of gasolines. Rhenium‐containing nickel‐based alloys are used for aircraft turbine engines.

Rhenium forms a wide variety of compounds in oxidation states

\documentclass{article}\pagestyle{empty}\begin{document}${{\rm{-}}1}$\end{document}

to

\documentclass{article}\pagestyle{empty}\begin{document}${{\rm{+}}7}$\end{document}

. High oxidation state compounds are common; low oxidation state compounds are restricted primarily to metal carbonyls and derivatives. Polynuclear compounds having strong metal–metal bonds are plentiful. Little is known concerning the toxicity of rhenium or its compounds.
Rheological Measurements
Authors: Schoff Clifford K. , Kamarchik Peter
Published: July 2004

This article is concerned with the experimental measurement of rheological properties of both liquids and solids and the principles on which these measurements are based. The flow properties of a liquid are defined by its resistance to flow, ie, viscosity. This concept is defined and discussed in terms of both theoretical flow models and practical consequences. Temperature, thixotropic and other time dependence, and concentration effects are covered for dilute polymer solutions, melts, and dispersed systems. Techniques and viscometers for capillary, rotational, and moving‐body measurements are described.

The rheological properties of elastic solids are made up of a combination of permanent deformation and recoverable elastic deformation. Additionally, a number of liquids show elastic as well as flow behavior. Mechanical models for this viscoelastic behavior are discussed. Also described are additional techniques beyond those indicated for simple solids and liquids, which are needed for complete characterization of mechanical behavior of materials in terms of elasticity and viscoelasticity. Examples of such methods are the dynamic measurement of response to sinusoidal oscillatory motion; the measurement of flow with time after application of stress, ie, creep; and the measurement of the rate and degree of recovery after removal of stress, ie, creep recovery or recoil. Special topics such as the Weissenberg Effect, time–temperature superposition, and electrorheological behavior are also discussed.
Riboflavin (B2)
Authors: Yoneda Fumio
Published: July 2004

Riboflavin (vitamin B2) has the chemical name 7,8‐dimethyl‐10‐D‐ribitylisoalloxazine, C17H20N4O6, mol wt 376.37. Riboflavin generally fulfills its metabolic function in the form of flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), and other covalently bound flavin derivatives, which serve as the prosthetic groups (coenzymes). They combine with specific proteins (apoenzymes) to form flavoenzymes, in a series of oxidation–reduction catalysts widely distributed in nature.

As a coenzyme component in tissue oxidation–reduction and respiration, riboflavin is distributed in some degree in virtually all naturally occurring foods. Liver, heart, kidney, milk, eggs, lean meats, and fresh leafy vegetables are particularly good sources of riboflavin.

In 1935, Karrer and Kuhn independently proved that riboflavin was 7,8‐dimethyl‐10‐D‐ribitylisoalloxazine by total syntheses. For therapeutic use, riboflavin is produced by chemical synthesis, which consists of the condensation of 4,5‐dimethyl‐2‐p‐nitrophenylazo‐1‐D‐ribitylaminobenzene with barbituric acid in an acidic medium, whereas the concentrates for poultry and livestock feeds are manufactured by fermentation using microorganisms such asAshbya gossypiiandEremothecium ashbyii.

Riboflavin is essential for mammalian cells. A lack of it in the human diet causes well‐defined syndromes, such as sore throat, hyperemia and edema of the pharyngeal and oral mucous membranes, cheilosis, angular stomatitis, and glossitis. A healthy adult requires ca 1.5–1.8 mg of riboflavin daily.

Derivatives include FMN, FAD, covalently bound flavins, 6‐hydroxyriboflavin, reseoflavin, and 5‐deazariboflavin.
Roofing Materials
Authors: Garcia Ruben G. , Corbin Ray L. , Gillenwater Richard J. , Compton Jim , Patenaude Cliff , Anthony Brian , Hunter Jim
Published: July 2004

Roofs are a basic element of shelter. As larger and larger roofing structures are desired, building designs become an important element in construction. A modern design normally includes a structure to carry loads, insulation to control heat flow, a barrier to control air and vapor flow, and a roofing element to prevent water penetration. This article discusses all aspects of roofing materials, from manufacturing methods, roofing system performance, specifications and application rates, to economic as well as health, safety, and environmental factors.
Rubber Compounding
Authors: Klingensmith William , Jenkins Frank , Klamp Walter , Fath Michael , Baranwal Kris , Ohm Robert , Russel Fell Ray , Rodgers Brendon
Published: July 2004

Rubber compounding combines the art and science of selecting the best combination of elastomer and other ingredients that meet the processing, cost, and performance requirements for rubber goods made and used in commerce. Chemical and physical properties of the wide variety of elastomers and ingredients available in making rubber goods are provided. Vulcanization, oils, plasticizers, general compounding, curing, fillers, latex, and testing are discussed.
Rubber Chemicals
Authors: Ohm Robert F.
Published: July 2004

Rubber chemicals are materials that are added in minor amounts to rubber formulations in order to improve their properties and make them commercially useful. Raw rubber polymer has very limited practical applications because of tackiness, flow, and other undesirable features. Rubber chemicals are added to assist processing, promote cross‐linking, and provide longevity to the part in service. Vulcanizing adjacent polymer chains together by cross‐links prevents flow, increases strength, and provides recovery from deformation. The most widely used method of cross‐linking polymer chains is by heating with elemental sulfur (vulcanization). Accelerators speed up the reaction of sulfur with polymer to improve the economics of manufacture and prevent degradation that would otherwise occur upon prolonged heating. Peptizers and process aids assist flow during the mixing and shaping operations. Antidegradants protect the part in service from heat, oxygen, ozone, and repeated flexing. Other rubber chemicals function as blowing agents, adhesion promoters, and activators or retarders which modify the onset of cross‐linking. Organic chemicals which are used primarily in the rubber industry contributed $415 million to the United States economy in 1994. Other rubber chemicals are also discussed.
Feeds and Feed Additives, Ruminant Feeds
Authors: Perry Tilden Wayne
Published: July 2004

This article discusses feedstuffs and feed additives that are incorporated into ruminant diets based on various physiological states of the animal. The ruminant animal is unique because it can utilize highly fibrous feedstuffs that are unsuitable for consumption by monogastric animals. Primary feedstuffs include forages/roughages, high energy feeds, supplements, feed additives, and juvenile animal feeds. Forages/roughages (fibrous feeds) are the predominant feedstuffs consumed by ruminants throughout the major portion of their lifetimes. Ruminants consume fibrous feeds either by grazing or by being fed preharvested forage. High energy feeds are those that are more energy dense than forages/roughages. These consist primarily of readily fermentable carbohydrate sources (grains) and lipids—either of plant or animal origin. A large number of supplemental sources of protein, energy, macrominerals, microminerals, and vitamins are discussed. Primary classes of feed additives include ionophores, ion‐exchange compounds, direct‐fed microbials, bloat preventatives, ruminal buffers, hormones, and antibiotics. Situations in which young ruminants consume feed other than mother's milk are discussed. Various feed sources for these young animals are identified. Because of the extreme diversity in ruminant production systems, the sources of ruminant feeds are extremely diverse.
Salicylic Acid and Related Compounds
Authors: Thomas Mary R.
Published: July 2004

Salicylic acid, also known aso‐hydroxybenzoic acid, appears early in the historical recognition of the identity and preparation of organic compounds. The extract of roots, bark, leaves, and fruit of many plants and trees contains the glucosides of methyl salicylate and other derivatives from which salicylic acid is easily derived by extraction and mild oxidation. The extract of willow bark was referenced by Hypocrites about 400BCas a pain reliever, and the preparation and crude estimate of strength were cited in the firstUnited States Pharmacopeiapublished in 1820.

Related to salicylic acid as isomers arem‐hydroxybenzoic acid andp‐hydroxybenzoic acid. The three are commonly known as the monohydroxybenzoic acids, which share chemical reactions and are used in a broad range of applications from paper coatings and liquid crystal preparations to drugs. Salicylic acid and its derivatives have demonstrated activity as analgesics, antipyretics, and antiinflammatory agents; para‐substituted acids and esters have activity as preservatives for food.
Sampling
Authors: Davies Reg
Published: July 2004

Davies, Reg (E. I. du Pont de Nemours & Co., Inc.). Sampling operations remove a portion of material from a free‐flowing or stationary assembly. The ideal is that this sample is representative of the bulk material. Sampling has grown in importance in response to the emphasis on environmental control and quality assurance. For pure liquids and gases, and solids of uniform particle size, sampling is relatively easy. Once fluids contain particulates, however, the sampling situation becomes more difficult. Particles of nonuniform size tend naturally to segregate. Sampling methods must be employed that circumvent these obstacles to ensure representative sampling. Methods of sampling gases, liquids, and solids are outlined. A discussion of gaseous sample treatments is presented as is liquid sample storage and treatment. Sample efficiency is introduced. Vol. 21, pp. 626–650, 32 refs. to October 1996.
Sealants
Authors: Palmer Richard A. , Klosowski Jerome M.
Published: July 2004

Sealants are materials installed in gaps or joints to prevent water, wind, dirt, or other contaminants from passing through the joint or gap. They are commonly rated by their movement ability. High movement sealants such as silicones, urethanes, and polysulfides typically accommodate joint movement of 25% or higher. Acrylic sealants are commonly used in joints where movement is 5–15% and no higher than 25%. Butyl sealants are used in applications with movement of

\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${<{\hskip-0.167em}{\hskip-0.167em}12.5{\%}}$\end{document}

. Each sealant type's base polymer provides inherent properties that find use in specific applications. Silicones are resistant to weathering and are used in applications where longevity is a prime concern. Urethanes are tough, abrasion‐resistant, with good adhesion to many substrates, thus allowing many applications in weatherproofing, especially in high abuse areas. Polysulfides have superior chemical resistance and find wide use in aircraft applications. Latex acrylics have good weatherability, low cost, and are easy to use, making them popular with consumers in nondemanding applications. Polyisobutylene sealants have low moisture vapor permeability and high tack, which are necessary for automotive and insulating glass applications.
Semiconductors, Organic
Authors: Sibley Scott P.
Published: July 2004

Semiconductors are materials that are characterized by resistivities intermediate between those of metals and of insulators. The study of organic semiconductors has grown from research on conductivity mechanisms and structure–property relationships in solids to include applications‐based research on working semiconductor junction devices. Organic materials are now used in transistors, photochromic devices, and commercially viable light‐emitting diodes, and the utility of organic semiconductors continues to increase.

The study of organic semiconductors and conductors is highly interdisciplinary, involving the fields of chemistry, solid state physics, engineering, and biology. This article provides a treatment of the theoretical aspects of organic semiconductors as well as an overview of recent advances in the field and the uses of these materials based on their conductive and optical properties.
Separations Process Synthesis
Authors: Barnicki Scott D. , Siirola Jeffrey J.
Published: July 2004

Separations process synthesis is the invention of conceptual flow sheets for the separation of multicomponent mixtures. Systematic methods are available to aid in the generation of separations schemes for analysis and evaluation. For fluid systems, distillation remains the separation method of choice. This article describes heuristic methods for generating alternative distillation schemes for nonazeotropic mixtures as well as a more general method for generating separation schemes for nonideal liquid mixtures including systems involving azeotropes. This latter method makes use of the residue curve map representation for vapor–liquid equilibria and introduces the concepts of strategic and opportunistic operations to systematically overcome difficulties introduced by azeotropes and other nonidealities. Mention is also given to separation synthesis methods for gas or vapor mixtures and for systems which involve dissolved solids.
Hormones, Sex Hormones
Authors: Gunnet Joseph W. , Dixon Lisa A.
Published: July 2004

Progestins are a class of steroids named for their role in maintaining pregnancy. Naturally occurring progestins, such as progesterone, are 21‐carbon steroids having the basic pregnane structure. Synthetic progestins are derived from four structural groups; ie, 5α‐prenanes, 5α‐androstanes, estranes, and gonanes. They are produced by chemical and microbial degradation of naturally occurring steroids and by total synthesis. Structure–activity relationships of progestins have been explored using computer‐aided techniques. The principal use of progestins is in contraception, prescribed alone or in combination with estrogens, where they act primarily to prevent uncontrolled estrogen stimulation of the uterine endometrium. Progestins have other uses based on their antiestrogenic effects. They are known to cause a conformational change in receptors. When bound to an agonist, progestin receptors act as transcription factors, altering the rate of expression of various genes. New antiprogestins with improved receptor specificity are becoming available and may eventually be used in some of the same therapeutic areas as progestin agonists.
Shape‐Memory Polymers
Authors: Lendlein Andreas , Kelch Steffen
Published: July 2004

Shape‐memory polymers
are stimuli‐responsive materials. Upon exposure to an external stimulus, they have the capability of changing their shape. A change in shape initiated by a change in temperature is called
thermally induced shape‐memory effect
. The shape‐memory effect results from the polymer's structure, ie, its morphology in combination with a certain processing and programming technology.

The polymer is processed into its permanent shape by conventional methods. Afterward, it is deformed and the desired
temporary shape
is fixed. The later process is called
programming
. Heating the programmed polymer above a temperature higher than the
transition temperature
,

T
trans

, results in activating the shape‐memory effect. Consequently, the recovery of the memorized, permanent shape can be observed. The described effect is called a
“one‐way” shape‐memory effect
.

The shape‐memory effect can be quantified by
cyclic thermomechanical investigations
. Important quantities describing the shape‐memory properties of the material for a certain strain σ
m
are the
strain recovery rate
,
R
r
and the
strain fixity rate, R
f
. The parameter
R
r
quantifies the ability of the material to memorize its permanent shape. The parameter
R
f
describes the ability of the material to fix the mechanical deformation ɛ
m
, which has been applied during the programming process.
Silicon Compounds, Silanes
Authors: Arkles Barry
Published: July 2004

Silanes are silicon compounds that can be divided into five important industrial groups: those containing Si–H (hydride functional silanes), Si–X (halosilanes), Si–C (organosilanes), Si–OSi (siloxanes), and Si–OR (silicon esters). Inorganic and organic hydride and halogen functional silanes are discussed. Physical and chemical properties are covered as are their manufacture and application in such areas as feedstocks for other classes of silicon compounds, fumed silica, and semiconductor silicon and silicones. Economic aspects of the production and utilization of silanes include estimates of semiconductor‐grade silicon production.
Silicon Compounds, Silicon Halides
Authors: Collins Ward
Published: July 2004

All of the halogens form single and mixed silicon halides. Monomeric silicon halides and halohydrides are generally tetrahedral compounds. A large number of halogenated polysilanes are also known. The only compounds of industrial importance are tetrachlorosilane and trichlorosilane. Both are used as precursors: the former primarily for high purity fumed silica; the latter for organosilanes and semiconductor‐grade silicon metal. Dichlorosilane, a by‐product of the other chlorosilanes, also finds use in the semiconductor industry.
Silicones
Authors: Butts Matthew , Cella James , Wood Christina Darkangelo , Gillette Gregory , Kerboua Rachid , Leman John , Lewis Larry , Rubinsztajn Slawomir , Schattenmann Florian , Stein Judith , Wicht Denyce , Rajaraman Suresh , Wengrovius Jeffrey
Published: July 2004

Silicon are a class of materials with unique properties that make them useful in a variety of applications of commercial interest and support a thriving global industry. This article updates a comprehensive survey of the chemistry and technology of silicones last published in Kirk‐Othmer Encyclopedia of Chemical Technology in 1997. The update contains more than 235 references not cited in the previous version and includes literature published through 2001. A new section dealing with fiber finishing applications has been included in the current version. The review provides an excellent primary reference for this interesting area of chemistry and technology.
Silver Compounds
Authors: Etris Samuel F. , Cappel C. Robert
Published: July 2004

Most silver compounds are made from aqueous silver nitrate, which in turn is made from silver metal. Silver compounds are found in nature, but are neither ubiquitous nor prevalent. Silver salts are therefore expensive. Much of the silver produced annually in the United States comes from recycled metal. The primary usage of silver compounds occurs in the photographic industry. Silver compounds are also utilized in batteries, as catalysts, to form the reflective backings of mirrors, and for electroplating silver. Silver(I) compounds and complexes are the most stable, although some materials of higher silver oxidation are known. Some aqueous silver solutions serve as antiseptics; others as analytic reagents.
Silicon Compounds, Silylating Agents
Authors: Pape Peter G.
Published: July 2004

Silylating agents are used to replace active hydrogens from the surface of organic materials by trisubstituted silyl groups. This procedure is effected for a variety of reasons. Simple organic compounds may be silylated for purposes of synthesis and analysis; inorganic mineral surfaces may be silylated for purposes of analysis, adhesion, and water repellence; metal oxides, glass, resins, enzymes, etc, may be silylated to effect corrosion resistance, antimicrobial activity, immobilization for catalysis, chromatography column material, waterproofing, etc. The various compounds and the methods utilized for silylation are discussed.
Separation, Size Separation
Authors: Luckie Peter
Published: July 2004

Size separation, an important industrial unit operation, is a solid–solid separation process that produces minimally two streams from a feed stream of particles: one of coarser particles and one of finer particles. Devices that perform such separations fall into two general categories: those that separate by passing particles through apertures (screening) and those that separate using the forces of fluid dynamics (classification).

The performance of a separating device can be characterized by its size selectivity curve which, in turn, can be characterized by three parameters that describe completely the separation capability of a device. These parameters, which depend on the size of particles as well as on the design of the equipment, can also be used to predict the separation.

Size separation devices include inclined vibrating and stationary screens, probability screens, settling‐pool classifiers, hydrocyclones, mechanical classifiers, free and forced vortex classifiers, and transverse flow classifiers. The separation achieved by a single unit can be improved by staging several units in prescribed configurations. Pneumatic classification systems should be designed to handle hazardous dust.
Size Reduction
Authors: Prior Michael
Published: July 2004

Size reduction is an extremely important unit operation, whereby materials are subjected to stress in order to reduce the size of individual pieces. The stress is applied by transmitting mechanical force to the solid.

This article covers particle breakage and fracture mechanics, models predicting grindability and energy requirements, prediction of particle‐size distribution, and methods of applying stress. Stress can be applied by impact, crushing, cutting, or by stressing the surrounding medium, or by nonmechanical methods. The principal properties of particles that need to be considered in size reduction are toughness/brittleness, hardness, abrasiveness, feed size, cohesity, particle shape and structure, heat sensitivity, toxicity, explodability, and specific surface.

Typical size‐reduction equipment includes jaw crushers, roller mills, cone crushers, ball mills, rod mills, hammer mills, pin disk mills, turbine mills, jet mills, and cutting mills. Wet grinding is also employed.
Smart Materials
Authors: Harvey James A.
Published: July 2004

From a technical and simple point of view a smart material is a material that responses to its environments in a timely manner. To expand on this definition a smart material is one that receives, transmits, or processes a stimulus and responds by producing a useful effect, which may include a signal that the material is acting upon it. Stimuli may include strain, stress, temperature, chemicals, an electric field, a magnetic field, hydrostatic pressures, different types of radiation, and other forms of stimuli. Transmission or processing of the stimulus may be in the form of an absorption of a photon, of a chemical reaction, of an integration of a series of events, of a translation or rotation of segments within the molecular structure, of a creation and motion of crystallographic defects or other localized conformations, of an alteration of localized stress and strain fields, and of others. The useful effects produced could be a color change, an index of refraction change, a stress or strain distribution change or a volume change. Also, incorporation within the definition of smart materials is the ability to be reversible.

Under the proper set of environments and circumstances all materials are smart and depict smart behavior at some point during their life cycle. Some examples of technically smart behaving materials given in this article are piezoelectric materials, electrostrictive materials, magnetostrictive materials, electrorheological materials, magnetorheological materials, thermoresponsive materials, pH‐sensitive materials, uv‐sensitive materials, smart polymers, smart gels (hydrogels), smart catalysts, and shape memory alloys.
Soap
Authors: Bartolo Robert G. , Lynch Matthew L.
Published: July 2004

Soap, in the strictest terms, is defined as the alkali salt of fatty acid. In industrial terminology, soap usually refers to the subset of monocarboxylate salts of at least eight carbons in length. However, in more contemporary vocabulary, soap has come to represent a myriad of commercial products: bar soap, liquid soap, laundry soap, etc, many of which are no longer wholly based on carboxylate salts. This article discusses the chemical and physical properties as well as production of carboxylate soaps, focusing particularly on the use of soap for personal cleansing products.

The term soap refers to the group of neutralized long‐chain carboxylic acids and have the general chemical form\documentclass{article}\pagestyle{empty}\begin{document}${CH_{3}\left({{\rm{CH}}{_{2n}}{\rm{COO}}{^{-}}{\rm{M}}{^{+}} }\right)}$\end{document}, where\documentclass{article}\pagestyle{empty}\begin{document}${{\rm{M}}{^{+}}}$\end{document}represents a cation such as sodium. The chain length of the aliphatic group is typically between seven and 21 carbons with one carboxylate carbon, yielding a molecule containing between eight and 22 carbons. The cation associated with the head group is generally sodium or potassium; however, other counterions can also be utilized, such as triethanolamine, heavy metals, alkali‐earth, or other alkali metals, such as magnesium or lithium. Sodium dodecanoate, CH3(CH2)10COONa, commonly named sodium laurate, is a good example of a simple soap.
Sodium Chloride
Authors: Bertram Bruce M.
Published: July 2004

Sodium chloride or common salt is produced by the mechanical evaporation of solution‐mined brine, solar evaporation of seawater or natural brines, and the underground mining of the mineral halite. Salt deposits are widely distributed in nature as bedded deposits and salt structures or diapirs (salt domes). Sodium chloride has physical and chemical properties that make it useful for many purposes, including cooking and food processing, highway deicing, water treatment, animal nutrition, chemical production, and industrial processing. Salt is a low priced, bulk commodity varying in purity depending on the method of production. The United States and China are the world's two leading salt producers.

Salt, an essential mineral nutrient, provides the principal cation in plasma and body tissue fluids. Table salt is the principal carrier for iodine to prevent iodine deficiency. The relationship between sodium and high blood pressure is of concern. Salt is regarded as safe for use as a food additive.
Sodium Nitrite
Authors: Bortle Walter H.
Published: July 2004

Sodium nitrite, NaNO
2
, is a versatile industrial chemical having applications that are widely based on its oxidizing properties or its ability to yield nitrous acid on acidification. It is hygroscopic and quite soluble in water, but not in most organic solvents. Sodium nitrite is a moderately strong oxidizer and toxic by ingestion. It can react violently with some chemicals, evolves toxic NO

x

on decomposition, and can promote burning when exposed to fire. It may be derived from the reduction of sodium nitrate, but is typically manufactured by the absorption of nitrogen oxides into solutions of sodium hydroxide or sodium carbonate. Dry and liquid forms of the product in several grades are offered in bulk and a variety of packaging options. Dry products may be treated with an anticake. Typical assays are 99% NaNO
2
for dry and 42% NaNO
2
for liquid products. Sodium nitrite consumed domestically is primarily of U.S. origin, with some imports. The product is used in azo dyes, rubber chemicals, heat treating and heat‐transfer salts, meat curing, metal finishing, organic chemical syntheses, and as a corrosion inhibitor.
Sodium Sulfides
Authors: Bush David R.
Published: July 2004

Sodium hydrosulfide, sodium sulfide, and sodium tetrasulfide are somewhat interchangeable in many applications. Uses range from ore flotation to leather tanning and from pulp processing in kraft pulping to lubricant manufacture. The processes used to manufacture these compounds are described. Sulfide solubilities are discussed. U.S. production and prices for selected years are presented.