bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluorine Compounds, Inorganic, Sodium
Authors: Mueller Werner H.
Published: July 2004

Sodium has two fluorides: sodium fluoride, used in pesticide formulations and in the fluoridation of potable water supplies; and sodium bifluoride, used as a laundry sour and in the cleaning of stone and brick building faces. Physical and chemical properties are discussed.
Sodium Nitrate
Authors: Pokorny Ludwik , Maturana Ignacio
Published: July 2004

More than 85% of worldwide sodium nitrate production is supplied from natural deposits in Chile, South America; the rest is provided essentially as a by‐product from nitric acid plants. Sodium nitrate is used as a fertilizer and in a number of industrial applications, primarily as an oxidizing agent. These latter include the manufacture of glass, explosives, and charcoal briquettes, and the production of potassium compounds. Consumption of sodium nitrate for industrial uses has been rather steady, but production for use as fertilizer has declined. Various technical and industrial grades are available, in addition to the agricultural grade. Surface mining methods are used to mine the Chilean nitrate ore. Mineral recovery and processing procedures are described, as are the various purification steps. Synthetically produced sodium nitrate results from absorption of waste nitrous oxide gases in an alkaline solution.
Sodium Carbonate
Authors: Eggeman Tim
Published: July 2004

Sodium carbonate is a white crystalline solid also known as soda ash. Sodium carbonate deposits and brines exist around the world. It is readily produced from natural deposits and also by synthetic pathways. Production from Trona and the Solvay synthetic process account for the vast majority of current capacity. Annual world production is almost 44 × 106tons.

Soda ash is classified as a moderate health hazard. It is an essential ingredient in the production of glass, chemicals, soaps, detergents, pulp, and paper.
Soil Stabilization
Authors: Valentine Donald
Published: July 2004

This article describes two general methods to impart desired water control and physical and mechanical properties to soil profiles by chemical treatments. Chemical grouting is the practice of injecting liquids (chemical grouts) containing organics and/or inorganics that solidify to form strong, water‐impermeable barriers into soil, rock, or concrete. Organic systems containing monomers that can polymerize or soluble polymers that can cross‐link into insoluble gels are most often used grouts. Grouts comprising polyacrylamides and polyurethanes are in common use. Typical applications include construction and repair of buildings, dams, shafts, etc. Chemical soil conditioning is the use of chemical treatments, typically with polymers, to improve the ability of soils to support vegetative growth in large‐scale agriculture, horticulture, and urban applications. Some soil conditioners help create and/or stabilize larger soil aggregates, reducing erosion and improving the efficiency of irrigation water use. Others are used to provide water reservoirs in the soil to facilitate agriculture in drier locations. Still others coat and stabilize soil surfaces against wind and water erosion. Many soil conditioners are similar to the polymeric systems formedin situby chemical grouts. The most commonly used soil conditioners are acrylic polymers, especially copolymers of acrylamide and sodium acrylate.
Solar Energy
Authors: Stokes Robert A.
Published: July 2004

Technology for converting the various forms of solar energy to fuels, electricity, or even valuable chemicals is presented. Commercial interest is increasingly focused on a small number of promising technologies for the supply of conventional transportation fuels and grid‐connected electricity. Five technologies are reviewed focusing on developments in the technology of solar energy conversion and progress toward cost goals which must be achieved in order for solar energy to compete with conventional sources of energy without subsidies. Increased world utilization of solar energy is a certainty in the twenty‐first century. Greater near‐term utilization of solar energy forms depends on cost and the availability of conventional fuels.
Sol–Gel Technology
Authors: Hench Larry L. , Orefice Rodrigo
Published: July 2004

The sol–gel process, which has a potentially high technological value, enables materials having unique structures and properties seldom obtained by other processing methods to be produced. Materials prepared by sol–gel technology are of very high purity and homogeneity, having controlled multiphase microstructures, net‐shape forming, and as‐cast surface features made at lower temperatures than those used for other processes. High purity metal alkoxides are employed as precursors for the synthesis of nanometric entities dispersed in a liquid environment or sol that eventually forms a gel. The nanostructure of the gel can be tailored by controlling the chemical reactions involving the precursors.

The steps of sol–gel processes for silica‐ and alumina‐based materials are discussed. Sol–gel technology involves precursor mixing and formation of a colloidal suspension, generally followed by a casting operation in which the low viscosity sol is introduced in molds. Aging provides the required mechanical property for further handling. Following aging, the solvents within the pores are eliminated by drying. A stabilization step is also required to eliminate any residual chemisorbed water. Production of a fully dense body involves a densification step at higher temperatures when the porosity is reduced to zero. Application of the sol–gel process include preparation of porous and dense monoliths, silica and alumina fibers, ceramic thin films, biomedical devices, and organic–inorganic hybrid composites. Many of the materials prepared by sol–gel technology are nanostructed. The majority of these substances are multicomponent. The various compositional possibilities are presented.
Solvent Recovery, Condensation
Authors: Frank Otto
Published: July 2004

It had been noted in the previous edition of this
Encyclopedia
, that removing solvents by condensing them from an inert gas in a water‐cooled condenser is inefficient, and may create a potentially hazardous condition at the point of discharge. Vapor pressures of most solvents are relatively high. Therefore, at temperatures obtainable in a water‐cooled heat exchanger these substances maintain an appreciable partial pressure in the discharging gas. An environmentally unacceptable high VOC (volatile organic compound) level in the emitted gas, and the fact that the remaining solvent concentration is in many cases above the lower explosive limit, makes a water‐cooled heat exchanger an unlikely instrument for solvent recovery.
Sonochemistry
Authors: Suslick Kenneth S.
Published: July 2004

Ultrasonic irradiation of liquids causes high energy chemical reactions to occur, often with the emission of light. The origin of sonochemistry and sonoluminescence is acoustic cavitation: the formation, growth, and implosive collapse of bubbles in liquids irradiated with high intensity sound. The collapse of bubbles caused by cavitation produces intense local heating and high pressures, with very short lifetimes. In clouds of cavitating bubbles, these hot‐spots have equivalent temperatures of roughly 5000 K, pressures of about 1000 atmospheres, and heating and cooling rates above 10
10
K/s. In single‐bubble cavitation, conditions may be even more extreme. Thus, cavitation can create extraordinary physical and chemical conditions in otherwise cold liquids.

Sonochemistry can be roughly divided into categories based on the nature of the cavitation event: homogeneous sonochemistry of liquids, heterogeneous sonochemistry of liquid–liquid or liquid–solid systems, and sonocatalysis (which overlaps the first two). In some cases, ultrasonic irradiation can increase reactivity by nearly a million‐fold. Because cavitation can only occur in liquids, chemical reactions are not generally seen in the ultrasonic irradiation of solids or solid‐gas systems.

Sonoluminescence in general may be considered a special case of homogeneous sonochemistry; however, recent discoveries in this field have heightened interest in the phenomenon in and by itself. Under conditions where an isolated, single bubble undergoes cavitation, recent studies on the duration of the sonoluminescence flash suggest that a shock wave may be created within the collapsing bubble, with the capacity to generate truly enormous temperatures and pressures within the gas.
Water, Sources and Quality Issues
Authors: Hem John D.
Published: July 2004

Factors affecting stream quality and general principles of stream water geochemistry are given. Ideally, water is controlled by the alteration of rock minerals through chemical weathering processes, which liberate soluble products. These processes are controlled or influenced by climatic factors, such as rainfall, air temperature, and evaporation associated with biological or biochemical processes. Human activity impacts water quality in an ever increasing manner. Carbon, sulfur, and nitrogen are present in the hydrologic cycle and their increase or decrease is an indication of water quality. The author has studied various drainage basins and water quality of these water supplies. One study, of the Great lakes–upper St. Lawrence River, is given as an example.
Spectroscopy, Optical
Authors: McDowell Robin S. , Kelly James F.
Published: July 2004

Spectroscopy, the study of electromagnetic radiation and its interaction with matter as a function of frequency or wavelength, is a versatile and powerful tool for investigating atomic and molecular structure, as well as for qualitative and quantitative analysis. Optical spectroscopy is surveyed emphasizing its applicability for qualitative and quantitative laboratory and process analysis and for monitoring atmospheric pollutants. Absorption, emission (from excited samples, and radiometry of ambient thermal emission), scattering (elastic and Raman), and luminescence (fluorescence and phosphorescence) spectroscopies are discussed for the different regions of the electromagnetic spectrum: radio and microwaves, mid‐ and near‐infrared, molecular ultraviolet–visible absorption, atomic absorption and emission, and x‐ray and gamma‐ray, in each case discussing instrumentation, sampling, and applications. Special techniques covered include null‐background detection, nonlinear Raman spectroscopy and other laser‐induced processes, optical activity, and Mössbauer spectroscopy. Modern ultrasensitive spectroscopies being developed for analytical use are briefly reviewed.
Sugar, Special Sugars
Authors: White J. S.
Published: July 2004

Although commercially sucrose is the most important sugar, there are other special sugars with special applications, among which fructose is the most important. Fructose, a monosaccharide consisting of one‐half of the sucrose molecule but having a sweetness 1.3–1.8 times that of sucrose, constitutes 4–8 wt % of many fruits, where it primarily occurs with glucose (dextrose) and sucrose. Maltose (malt sugar) is a disaccharide comprising two molecules of glucose. Although occurring in some plants and fruits, it is more frequently recognized as a structural component of starch. Lactose (milk sugar) is the only commercially available sugar that is derived from animal rather than plant sources. It is a disaccharide consisting of one galactose and one glucose moiety and has only one‐fifth the sweetening power of sucrose.
Sprays
Authors: Mao Chien‐Pei , Tate Roger
Published: July 2004

Sprays are widely used in many industrial processes. In more recent years, the subject of liquid atomization has developed from a position of minor importance into a broad and significant technology. This article summarizes nonproprietary information and covers such topics as liquid atomizers, physics of atomization, spray characterization, instrumentation, and industrial applications.

Atomizers have been summarized according to their sources of energy, distinct design features, and applications. Discussion of the physics of atomization is divided into three different regimes: internal flow, liquid breakup, and droplet dispersion. Spray characterization focuses on the explanation of common spray parameters, typical spray dynamic structures, effect of variables, and correlation techniques. Because of its important role, spray instrumentation is also discussed, along with an overview of representative optical and nonoptical techniques. Specific examples of industrial spray applications are cited and general comments are made regarding the proper selection of liquid atomizers and concerns related to their operation.
Fine Chemicals, Standards
Authors: Tuthill Samuel M. , Jamieson Norman C.
Published: July 2004

Standard setting in the United States for fine chemicals used as drugs, food additives, laboratory reagents, and in the processing of semiconductors is described, as are reference materials for use in analytical procedures. The specifications and methods of test which comprise the standards are published on a regular basis, with interim supplements as necessary, in the
United States Pharmacopeia (USP)‐National Formulary (NF), the Food Chemicals Codex, Reagent Chemicals‐ACS Specifications
, and the
Book of SEMI Standards
. Many test methods, especially those in the USP and NF, require reference standards, available from the USP and the National Institute of Standards and Technology (NIST). The legal status of the USP, NF, FCC, and ACS Standards is discussed, as well as the impact on fine chemicals of the Federal Food, Drug, and Cosmetic Act requirements for Good Manufacturing Practice.
Starch
Authors: Whistler Roy L. , Daniel James R.
Published: July 2004

Starch is the principal food reserve of plants and is commercially derived from grains and tubers. Starch is a mixture of two polysaccharides (glucans). The smaller of the two, amylose, is essentially a linear polymer composed of α‐D‐glucopyranosyl units linked (\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${1{\rm{\longrightarrow }}4}$\end{document}). The larger polymer is amylopectin which contains α(\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${1{\rm{\longrightarrow }}4}$\end{document}linkages and α\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${1{\rm{\longrightarrow }}6}$\end{document}) branch points. These polymers occur naturally in small structures known as starch granules. Many of the chemical and physical properties of starch depend on its granular nature.

Starch hydrolysis leading to molecular fragments varying from large molecular weights down to small oligosaccharides andD‐glucose may be accomplished by acids, enzymes, or a sequence of the two. Commercially important sweeteners, corn syrup and high fructose corn syrup, are produced by starch hydrolysis and in the case of HFCS its partial isomerization. Less severe acidic treatment produces acid‐modified (thin‐boiling) starch. Other common starch modifications include pregelatinized and oxidized starch.

Because of the high number of hydroxyl groups, starches may be chemically derivatized to produce hydroxyalkyl starch ethers, cationic starches, starch phosphates, and starch acetates. Depending on the derivative and the degree of substitution, these starches may have various food and nonfood uses. In foods they are used to thicken, gel, or otherwise control texture, whereas in nonfood uses they are important as sizing and finishing agents in both paper and textiles.
Steam
Authors: Bellows James
Published: July 2004

Steam is the most important industrially used vapor and, after water, the most common and important fluid used in chemical technology. It can be generated by evaporation of water at subcritical pressures, by heating water above the critical pressure, and by sublimation of ice. Steam is used in electric power generation; for driving mechanical devices; for distribution of heat; as a reaction medium; as a solvent; as a cleaning, blanketing, or smothering agent; and as a distillation aid. Steam not only has high latent heat, moderate density, and nonpolluting properties, but also provides easy control of temperature in processes and heating application.

Steam is generated from water by boiling, flash evaporation, and throttling from high to low pressure. The phase change occurs along the saturation line with the specific volume of steam larger than that of the boiling water. Thermal energy (heat of evaporation) is absorbed during the process. At the critical and supercritical pressures, the water–steam distinction disappears. The thermodynamic and physical properties of pure steam are well established over the range of pressures and temperatures used. Corrosion of containment materials and purity of water are important to steam production.
Stilbene Dyes
Authors: Smith Roy E.
Published: July 2004

Stilbene dyes of importance are mostly direct yellow dyes for cellulosic fibers, especially paper. There have been several red and blue stilbene‐containing dyes reported but none have been developed to commercial importance. There are brown leather dyes which are stilbene‐based.

Most stilbene dyes are derived from 4‐nitrotoluene‐2‐sulfonic acid which is oxidized under alkaline conditions to 4,4′‐dinitro‐2,2′‐stilbenedisulfonic acid, which can be further condensed to yellow dyes or reduced to 4,4′‐diamino‐2,2′‐stilbenedisulfonic acid. The latter can be tetrazotized and coupled to yield dyes of reasonably definitive structure. 4,4′‐Diamino‐2,2′‐stilbenedisulfonic acid is more important as an intermediate for fluorescent brighteners than for dyes. Dyes produced by alkaline condensation of 4‐nitrotoluene‐2‐sulfonic acid or 4,4′‐dinitro‐2,2′‐stilbenedisulfonic acid are listed as a subclass of azo dyes. Those dyes derived from coupling the tetrazo of 4,4′‐diamino‐2,2′‐stilbenedisulfonic acid are listed as regular azo dyes.

Since 1980 activity has been reported in all known areas of stilbene dye chemistry, but it is minuscule compared to other dye chemistries. There were reports of using 4,4′‐diaminostilbene‐2,2′‐disulfonic acid as a bridging group in reactive dyes and one report of stilbene participating in the chromophore. Basic dyes reported were made by coupling the tetrazo of 4,4′‐diaminostilbene and quaternizing.

The most important stilbene dyes are those known for more than fifty years. The commercial importance of Direct Yellow 11 (1883), Direct Orange 15 (1888), Direct Yellow 4 (1886), and Direct Yellow 106 (1936) attests to the value, properties, and durability of stilbene yellow dyes.
Carbon, Survey
Authors: Long J. C. , Criscione J. M.
Published: July 2004

Elemental carbon, atomic number six in the periodic table, at wt 12.011, occurs naturally throughout the world in either its crystalline (more ordered) or amorphous (less ordered) form. Carbonaceous materials such as soot or charcoal are examples of the amorphous form, whereas graphite and diamond are crystalline. Carbon atoms bond with other carbon atoms as well as with other elements, principally hydrogen, nitrogen, oxygen, and sulfur, to form carbon compounds, which are the subject of organic chemistry. In their many varying manufactured forms, carbon and graphite can exhibit a wide range of electrical, thermal, and chemical properties that are controlled by the selection of raw materials and thermal processing during manufacture. There are two allotropes of carbon: diamond and graphite. A wide variety and range of bulk carbon forms are available within the industry. In general, commercial forms are loosely characterized as carbon or graphite, but they are distinctly different. The termmanufactured carbonrefers to a bonded granular carbon body whose matrix has been subjected to a temperature typically between 900 and 2400°C.Manufactured graphiterefers to a bonded granular carbon body whose matrix has been subjected to a temperature typically in excess of 2400°C. Natural graphite has been known since the Middle Ages, but carbon was first fabricated by H. Davy in his experiments on the electric arc in the early 1800s. The manufacture of artificial graphite came about only at the end of the nineteenth century, preceded by developments in the fabrication of electrodes.

A useful form of graphite is a flexible sheet or foil. Carbon–graphite foam is a prime candidate for thermal protection of new, emerging carbon–carbon aerospace reentry vehicles. Pyrolytic graphite produced in massive shapes is used for missile components, rocket nozzles, and aircraft brakes for advanced high performance aircraft. Glassy, or vitreous, carbon is a black, shiny, dense, brittle material with a vitreous or glass‐like appearance. Carbon and graphite paper has outstanding electrical conductivity, corrosion resistance, and moderately high strength.
Styrene‐Butadiene Rubber
Authors: Lattime Richard R.
Published: July 2004

Lattime, Richard R. (The Goodyear Tire & Rubber Co.). Although produced in the 1990s, emulsion styrene–butadiene rubber (ESBR) only gained its manufacture prominence and acceptance as the substitute for natural rubber as a result of World War II. In the 1950s, the discovery of alkyllithium compound initiators gave stereospecific copolymers of styrene and butadiene. Control of the polymer microstructure of random solution styrene–butadiene rubber (SSBR) gave enhanced tire properties of improved rolling resistance, wet traction, and improved treadwear. SSBR began to displace ESBR in some tire applications in the early 1960s. ESBR and SSBR combine in the mid‐1990s to give the largest‐volume synthetic polymer manufactured, amounting to about 29% of the world consumption of all synthetic rubber.

Although both ESBR and SSBR processed somewhat differently from natural rubber, both polymer types were quickly adapted to the common rubber processing machinery. Recipes include the typical vulcanizing agents, accelerators, accelerator activators, pigments, softeners, and antidegradents. Worldwide production of styrene–butadiene rubber increased 7% from 1994 to 1995; projected growth through 1999 is 11%. This increase in a historically flat market is the result of increasing scarcity of natural rubber as plantations continue to be taken out of production. Tires remain the largest market for ESBR and SSBR, accounting for 80% of the total. At the end of 1995, rubber and tire manufacturers were required to comply with a section of the Clean Air Act Amendments of 1990 to report emission information of identified hazardous air pollutants specific to their operation.
Styrene Plastics
Authors: Fumagalli Carlo
Published: July 2004

Succinic acid and succinic anhydride occur frequently in nature. Their chemical behavior is characterized by the reactivity of the two carboxylic functions, ie, hydration/dehydration, esterification, hydrogenation, acylation, and reactions with nitrogen and sulfur compounds, as well as of the two methylene groups, ie, oxidation, halogenation, and condensation with aldehydes and ketones. Succinic anhydride is manufactured by liquid‐phase catalytic hydrogenation of maleic anhydride; succinic acid by hydration of the anhydride. The acid is also obtained as a by‐product in the manufacture of adipic acid. The total consumption of succinic acid and succinic anhydride in 1993 was in the 13,000–15,000 t/yr range; combined installed capacity is about 20,000 t/yr in 1994. Uses include bath preparations, detergents, cosmetics, pigments, fluxes for soldering, and reagents for the synthesis of pharmaceutical products. An important emerging use is the production of inherently degradable polymers. Succinic acid is an approved food additive having FDA generally‐recognized‐as‐safe status. Both the acid and the anhydride are irritating to the eyes, skin, and mucous membranes.
Sugar, Sugar Analysis
Authors: Godshall Mary An
Published: July 2004

Sugar analysis includes the determination of sucrose in raw sugar, along with other quality factors such as moisture, ash, and color, for trading purposes. It also includes the determination of reducing sugars in products of sugar manufacture and the determination of sugars in foods in general. Polarimetry, commonly called polarization in the industry, is the most widely used method for sugar analysis in commerce, and copper reduction methods are still commonly used for reducing sugars. Newer methods, such as chromatography, both gas and liquid, enzymatic technology, and near infrared spectroscopy have many advantages and are being used with greater frequency, especially for food and nutrition labeling and for process control in manufacturing.
Sugar, Sugar Derivatives
Authors: Khan Riaz , Konowicz Paul A.
Published: July 2004

Sucrose is an important food commodity. Its potential as a raw material for chemicals has long been recognized, but the actual commercial success has been limited. Significant progress toward the understanding of its chemistry has been made in recent years. This has led to the development of such commercial products as sucralose, a high intensity sweetener; sucrose fatty acid esters as food additives or emulsifiers and surfactants; and Palatinit and Actilite as noncariogenic bulk sweeteners.

The application of reactions such as esterification, etherification, sulfonylation, SN2 displacement reactions, halogenation, oxidation, and amination has resulted in a large number of well‐characterized sucrose derivatives. The potential of these derivatives as biologically active materials, polymer intermediates, food additives, as well as other industrial applications, awaits development.
Sugar Alcohols
Authors: Lawson Mary E.
Published: July 2004

The chemical, physical, and biological properties as well as the functional applications of sugar alcohols (polyols) are discussed in this article. Sugar alcohols are derived from sugars by catalytic hydrogenation to reduce an aldehyde or a ketone group of a sugar to a hydroxyl group. The sugar alcohols are classified as monosaccharide and disaccharide alcohols, with further subclassification of the monosaccharide alcohols according to the number of carbons they contain: tetritols, ie, erythritol; pentitols, ie, xylitol; and hexitols, ie, sorbitol and mannitol. The disaccharide alcohols discussed include maltitol, lactitol, and isomalt.

Unlike the corresponding sugars from which they are derived, sugar alcohols have the advantages of anticariogenicity (ie, they do not cause tooth decay), insulin‐independent metabolism, and lower caloric values. These properties have led to the use of sugar alcohols in a wide variety of sugar‐free applications, such as chewing gum, hard candy, chocolate coatings, and bakery.
Sulfur Removal and Recovery
Authors: Capone Michael
Published: July 2004

The removal and recovery of sulfur species is practiced to limit sulfur emissions to the environment and for larger sulfur capacities, to recover a valuable sulfur product. The most common applications are the removal of hydrogen sulfide and sulfur dioxide and subsequent conversion to elemental sulfur. Many processes have been developed for the recovery of each of these sulfur species, typically consisting of one or more of the following steps: adsorption of the hydrogen sulfide or sulfur dioxide on a solid; absorption of the sulfur species into a solvent via chemical reaction or physical gas–liquid solubility; and conversion of hydrogen sulfide or sulfur dioxide to elemental sulfur. Other, nonconventional processes are being developed such as thermal cracking of hydrogen sulfide to produce sulfur and hydrogen.
Sulfolane and Sulfones
Authors: Clark Earl
Published: July 2004

Sulfolane is a colorless, polar, water‐soluble, 4‐carbon, cyclic sulfone having exceptional chemical and thermal stability. Applications for sulfolane derive mainly from its polar solvent characteristics. It is used as a solvent or solvent component for aromatics extraction, gas treating, and extractive distillation processes, as well as a solvent for polymerizations and chemical reactions. It is also useful in plasticizer, electronic, and textile‐related specialty applications. Sulfolane is relatively chemically inert and exhibits low toxicity by all modes of administration. The chemical is available commercially in the anhydrous form or containing 3 wt % deionized water as a freezing point depressant. Other sulfones of commercial significance are also discussed. These include sulfolene, dimethyl sulfone, diiodomethylp‐tolylsulfone, 4,4′‐dihydroxydiphenyl sulfone, and bis(p‐chlorophenyl) sulfone.
Sulfurization and Sulfurchlorination
Authors: Duncan Michael P.
Published: July 2004

The mechanisms for the reaction of sulfur with alkanes and unsaturated compounds are highly speculative, but generally, unsaturated compounds are much more reactive toward sulfur than alkanes. Sulfur reacts with mercaptans in the presence of basic catalysts, forming polysulfides. Sulfur monochloride and sulfur dichloride react with both unsaturated materials and mercaptans. Sulfurized and sulfurchlorinated unsaturated compounds and mercaptans are used as lubricant additives, refinery catalyst regeneration compounds, steel processing aids, and vulcanization catalysts. Manufacturing methods for sulfurization of unsaturated compounds and mercaptans and for sulfurchlorination of unsaturated compounds or mercaptans are given. These products are normally considered nonhazardous.
Sulfur Dyes
Authors: Senior J. , Guest R. A. , Wood W. E.
Published: July 2004

Sulfur dyes are used mainly for dyeing textile cellulosic materials or blends of cellulosic fibers with synthetic fibers such as acrylic fibers, polyamides (nylons), and polyesters. They are also used for silk and paper in limited quantities for specific applications. Solubilized sulfur dyes are used on certain types of leather. From an application point of view, the sulfur dyes are between vat, direct, and fiber‐reactive dyes. They give good to moderate lightfastness and good wetfastness at low cost and rapid processing.

The quality of sulfur dyes has greatly improved mainly because well‐defined organic compounds are used as starting materials. Owing to better techniques, sulfur dyes have good storage stability and fastness properties, and are generally easily adaptable to modern dyeing methods. In the 1980s and 1990s, reduction of sulfide levels has been achieved.

Properties, classifications, structure, manufacture, applications, economic aspects, health and safety factors, and uses are all discussed.
Sulfur Compounds
Authors: Weil Edward D. , Sandler Stanley R.
Published: July 2004

Sulfur is a component of many compounds. Carbon sulfides, thiophosgenes, trichloromethanesulfenyl chloride, hydrogen sulfide, hydrogen polysulfides (sulfanes), sulfur halides and oxyhalides, sulfur nitrides, sulfur oxides, sulfur oxygen acids and their salts, thiocyanic acid and its salts, methanesulfonyl chloride, and methanesulfonic acid are all discussed, along with properties, manufacture, shipment and storage, economic aspects, analytical methods, grades and specifications, health and safety, and uses.
Supercritical Fluids
Authors: Dixon David J. , Johnston Keith P.
Published: July 2004

A supercritical fluid is characterized as a gas that is pressurized and heated to a compressed fluid state, which is above both the critical pressure and temperature of the gas. In this state, density and subsequently solvent strength are highly adjustable by modest changes in temperature and pressure. Complex phase behavior and interactions with materials can occur. This behavior can be examined experimentally and described successfully by molecular thermodynamics. Carbon dioxide and water are two substances used frequently as supercritical fluids. The former, which may be used independently or in the presence of various cosolvents, is predominantly used because of its environmentally benign nature and low cost. The latter is used because of its efficiency in destroying hazardous aqueous pollutants. Numerous supercritical fluid processes have been commercialized, including coffee and tea decaffeination, supercritical water oxidation, supercritical fluid chromatography, and the UNICARB spray coating process. Process research and development involving supercritical fluids are progressing in many diverse areas, including extraction of food, pharmaceuticals, or pollutants; fractionation of oils or polymers; biocatalysis or polymerization reactions; and material reformation or modification.
Supported Catalysts
Authors: Clark James H. , Macquarrie Duncan J.
Published: July 2004

Supported catalysts largely based on porous inorganic and organic support materials can be used in a wide range of important organic reactions for the preparation of fine and speciality chemicals. Major areas of research and application, notably solid acids, solid bases, and supported metal complexes, are covered in this article.
Surfactants
Authors: Lynn Jesse L. , Bory Barbara H.
Published: July 2004

The term surfactant is a contraction of surface‐active agent. Surfactant has become universally accepted to describe organic substances having certain characteristic features in structure and properties. The term detergent is often used interchangeably with surfactant. As a designation for a substance capable of cleaning, detergent can also encompass inorganic substances when these do in fact perform a cleaning function. More often, detergent refers to a combination of surfactants with other substances, organic or inorganic, formulated to enhance functional performance, specifically cleaning, over that of the surfactant alone. Surfactants are characterized by amphipathic structure, solubility, adsorption at interfaces, orientation at interfaces, micelle formation, and functional properties. Each is discussed, as are uses, production, and economic aspects.
Surface and Interface Analysis
Authors: Pemberton Jeanne E.
Published: July 2004

Surfaces are formed in the transition from one state of matter to another, whether the two phases are chemically distinct or not. Thus, surfaces exist at interphases or interfaces between two phases of either the same or different materials. Many important chemical processes occur at solid–solid, solid–liquid, solid–gas, liquid–liquid, liquid–gas interfaces.

The chemical, structural, and electronic characteristics of surfaces and interfaces are usually different from those of the bulk phase(s). Thus, methods to be used for the analysis of surfaces must be selective in response to the surface or interfacial region relative to the bulk. Surfaces and interfaces are most commonly explored using techniques based on the interaction of photons, electrons, or ions with the surface or using a force such as electric field or Van der Waals attraction. These excitations generate a response involving the production of photons, electrons, ions or the alteration of a force that is then sensed in the analysis.

A plethora of characteristics of surfaces and interfaces can be analyzed using a staggering variety of techniques.

Several methods utilizing photons as the exciting and detected species are commonly employed such as transmission ftir spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy (drift), infrared reflection‐absorption spectroscopy (irras), Raman spectroscopy, surface enhanced Raman scattering (sers), or sum‐frequency generation (sfg).

Electrons are used for excitation and detection in the various electron microscopy methods for surface visualization and imaging. Techniques such as scanning electron microscopy (sem), field emission scanning electron microscopy (fe‐sem), transmission electron microscopy (tem), and scanning transmission electron microscopy (stem), the electron diffraction methods for the determination of surface atomic structure [low energy electron diffraction (leed), reflected high energy electron diffraction (rheed)], and the electron energy loss spectroscopies for evaluation of surface electronic and chemical characteristics [electron energy loss spectroscopy (eels), high resolution electron energy loss spectroscopy (hreels), and core level electron energy loss spectroscopy (ceels)] are discussed. Ions produced by electron‐stimulated desorption are measured in electron‐stimulated desorption ion angular distribution (esdiad). If neutralization of an incident ion beam is measured by surface electron ejection, the technique of ion neutralization spectroscopy (ins) results.

Ions can also be used as both the excitation and detection species in several surface analysis techniques which are also discussed.
Coating Processes, Survey
Authors: Cohen Edward D. , Gutoff Edgar B.
Published: July 2004

Coating process technology is used to produce a wide variety of products, such as surface coatings to protect houses, bridges, and automobiles; packaging materials to store food; adhesives for use in labels; photographic films; optical and magnetic media for audio and visual use data storage; glossy paper for magazines; and printing plates. The coating machine, which produces the coated web, has several steps. The web is unwound and transported through the coater, then a coating applicator applies the coating which is then solidified, and finally the web is rewound. The coating machine can also contain devices to modify the surface properties, to clean the web, to measure coating weight, and to laminate a second web to the structure.

Many of the commercially available coating applicators are described, including units for simultaneous multilayer application, for discrete coating, and for patch coating. While convection drying is emphasized, brief descriptions of conduction and infrared heating, as well as of uv and electron‐beam curing, are given.
Clays, Survey
Authors: Murray Haydn H.
Published: July 2004

Clay minerals and materials have very diverse physical and chemical properties dependent largely on their structure and composition. Clays are comprised of hydrous phyllosilicates called clay minerals. The phyllosilicates are generally platy in shape and differ from one another with regard to the structural arrangement of the layers, the water content, and the associated cations. The clay mineral groups are kaolins, smectites, illites, chlorites, and palygorskite‐sepiolite. The differences in these clays are discussed along with their origin and geographic locations.
Metallurgy, Survey
Authors: Hiskey Brent
Published: July 2004

Metallurgy is both an ancient art and a modern science, requiring detailed knowledge of the structure, properties, and behavior of metals and metal alloys. Whereas for many metals, the primary source materials are crude metalliferous ores, for some metals recycled material, ie, scrap, contributes significantly to total metal production. Extractive processes for ores or scrap, which may be physical or chemical and may include treatment for prevention of corrosion, processing of metals or alloys by heat treatment, casting, etc, and physical measurements relating to failure analysis and other structure/property relationships, are all areas of metallurgy. Terms used in metallurgy are defined. The relationship between ore grades, metal prices, and economic feasibility is discussed.
Metallic Coatings, Survey
Authors: Krulik Gerald A. , Mandich Nenad V.
Published: July 2004

Metallic coatings may be functional or decorative, permanent or temporary, sacrificial, or noble. Pure metals, metal alloys, metal compounds, and intermetallics may be used. The base material to which the metallic coating is bonded may be metallic, nonmetallic inorganic, or an organic such as a plastic, paper, or a fiber. Methods for metallic coating may be divided according to the way the metal is applied: liquid phase, gas phase, and vacuum phase metallizing, and metallizing by direct physical or thermal bonding. The various processes in each of these categories are described, along with the types of coatings and base materials used. Environmental considerations of these coating processes are also discussed.

Whereas galvanizing and electroplating represent the processes having the largest volume of metallic coated materials, the gas and vacuum phase metallizing processes used in the electronics industry represent the highest economic value. The corrosion and wear resistance of metallic coated tools and parts is of the utmost industrial importance.
Hydrocarbons, Survey
Authors: Mears David E. , Eastman Alan D.
Published: July 2004

Hydrocarbons, compounds of carbon and hydrogen, are structurally classified as aromatic and aliphatic; the latter includes alkanes (paraffins), alkenes (olefins), alkynes (acetylenes), and cycloparaffins. Hydrocarbons are important sources for energy and chemicals and are directly related to the gross national product. The United States has led the world in developing refining and petrochemical processes for hydrocarbons from crude oil and natural gas.

Hydrocarbons are used in the production of lubricants, in agriculture and food, in coatings, and in polymers. Toxicity and regulatory issues, including U.S. Clean Air Acts, the Clean Water Act, the Resource Conservation and Recovery Act, and others are discussed.
Elastomers, Synthetic, Survey
Authors: Morton Maurice
Published: July 2004

The purpose of this article is to provide a brief overview of the materials designated synthetic elastomers and the elastomeric or rubbery state. Subsequent entries describe the individual classes of elastomers in detail. The principal classes of synthetic elastomers covered here or elsewhere in theEncyclopediaare acrylic elastomers, butyl rubber, chlorosulfonated polyethylene, ethylene‐propylene–diene rubber, fluorocarbon elastomers, nitrile rubber, polybutadiene, polychloroprene, polyethers, polyisoprene, styrene‐butadiene rubber, thermoplastic elastomers, silicones, polysulfide rubber, and polyurethanes.
Acrylic Ester Polymers
Authors: Slone Robert V.
Published: July 2004

The nature of the R group in its formula determines the properties of each acrylic ester and the polymers it forms. Polymers of this class are distinguished by their water‐clear color and stability on aging. Acrylic monomers are extremely versatile building blocks. They readily polymerize or copolymerize with a variety of other monomers. Copolymers with methacrylates, vinyl acetate, styrene, and acrylonitrile are commercially significant. Although the acrylics have a higher cost than many other monomers their unique characteristics and efficiency offset the higher cost. Acrylic ester polymers can be made to hydrolyze to poly(acrylic acid) or an acid salt and the corresponding alcohol. Two principal processes are used for the manufacture of monomeric acrylic esters: the semicatalytic Reppe process and the propylene oxidation process, the latter of which is preferred because of economy and safety. The toxicities of acrylic monomers range from moderate to slight. The vast majority of all commercially prepared acrylic polymers are copolymers of an acrylic ester monomer with one or more different monomers. Copolymerization has led to the development of many different resins for a variety of applications. Acrylic polymers are considered to be nontoxic, and are used primarily in coatings, textiles, adhesives, and paper.
Alcohols, Higher Aliphatic, Survey and Natural Alcohols Manufacture
Authors: Kenneally Corey J.
Published: July 2004

The monohydric aliphatic alcohols of six or more carbon atoms are generally referred to as higher alcohols. Historically, the higher alcohols were derived from natural fats, oils, and waxes and were called fatty alcohols, but now similar alcohols are widely available from synthetic processes using petrochemical feedstocks. Although the natural and synthetic alcohols are used interchangeably for many applications, for some applications the distinction still remains. The detergent range alcohols are used mainly as sulfate, ethoxy, and ethoxysulfate derivatives in a wide variety of detergent and surfactant applications. Most higher alcohols of commercial importance are primary alcohols; secondary alcohols have more limited specialty uses. Typical reactions of the higher alcohols include esterification, sulfation, etherification, halogenation, dehydration, oxidation, and amination. In the United States, most detergent range alcohol production is by synthetic processes. Most manufacturers sell a portion of their alcohol product on the merchant market, retaining a portion for internal use, typically for the manufacture of plasticizers. The higher alcohols are among the less toxic of commonly used chemicals. Fatty alcohols are produced by hydrogenolysis of methyl esters or fatty acids in the presence of a heterogeneous catalyst. There are three principal hydrogenolysis processes in worldwide use. Each process typically uses a copper chromite or copper‐zinc catalyst that is modified to meet the needs of the individual producer. The detergent range alcohols and their derivatives have a wide variety of uses in consumer and industrial products. The major use is as surfactants in detergents and cleaning products. They also are used extensively in cosmetics and pharmaceuticals. The plasticizer range alcohols are utilized primarily in plasticizers, but they also have a wide range of other uses.
Textiles, Survey
Authors: Rebenfeld Ludwig
Published: July 2004

Consumption trends of those fibers that are used in the production of typical apparel, household, and industrial textiles are classified and presented. Both naturally occurring fibers, such as cotton and wool, and manufactured fibers are discussed. For manufactured fibers, the methods of fiber production by extrusion spinning are described. The three principal types of textile fabrics, woven, knitted, and nonwoven, are defined and described, as are some of the important dyeing and finishing operations used in the textile industry.
Vitamins, Survey
Authors: Scott John W.
Published: July 2004

The vitamins are a group of organic substances, present in small amounts in foods, that are essential for normal metabolism in humans. Lack of vitamins results in deficiency diseases. More recent science indicates that there is another role for vitamins in the maintenance of optimal health. The 13 vitamins are divided into fat‐soluble and water‐soluble groups. The fat‐soluble vitamins include vitamin A (retinol), vitamin D (cholecalciferol), vitamin E (α‐tocopherol), and vitamin K (phylloquinone). The water‐soluble vitamins are vitamin B
1
(thiamine), vitamin B
2
(riboflavin), niacin (vitamin B
3
, nicotinic acid), vitamin B
6
(pyridoxine), vitamin B
12
(cobalamin), folic acid, pantothenic acid, biotin, and vitamin C (ascorbic acid). All are items of commerce resulting from isolation from natural sources, chemical synthesis, or fermentation. In addition to human health, a primary use of vitamins is in animal production.
Sutures
Authors: Lewis O. Griffin , Fabisiak Walter
Published: July 2004

Surgical sutures are sterile, flexible strands used to close wounds or to tie off tubular structures such as blood vessels. They may be made from natural or synthetic fibers and are usually attached to a needle. The generic and proprietary names of the natural and synthetic polymeric fibers used in the manufacture of surgical sutures distributed commercially in the United States are given, along with the claims for retention of strength at various intervals and the time required for absorption. The various structures of sutures are discussed in terms of biological compatibility, diameter and strength standards, and methods of sterilization. Color additives and coatings for each type of suture are described, as are the accompanying needles. Regulatory requirements are discussed, and tables of
United States Pharmacopeia
specifications are given.
Silica, Synthetic Quartz Crystals
Authors: Armington Alton F.
Published: July 2004

Silicon dioxide exists in both crystalline and glassy forms. The most common crystalline form is that of α‐quartz. Synthetic quartz crystals, free of twinning and other imperfections, are used extensively in electronic applications. The hydrothermal processing techniques used to synthesize commercial quantities of high purity quartz crystals are discussed. The reasons for using synthetic quartz as timing control and piezoelectric devices are presented.