bluuebunny/crossref_metadata_2025 huggingface dataset:
Aluminum Sulfate and Alums
Authors: Darragh K. V. , Ertell C. A.
Published: August 2004

Aluminum sulfate octadecahydrate,\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{Al}}{_{2}}{(} {\rm{SO}}{_{4}}{)}_{3}{\rm{{\cdot{}}}}18{\rm{H}}{_{2}}{\rm{O}}}$\end{document}, and its aqueous solutions are used primarily in the paper industry for sizing and as a flocculating agent in water and wastewater treatment. This material is often called papermakers' alum or alum and is sometimes referred to as cake alum or patent alum. The solid commercial hydrate also called dry alum, ground or lump. Anhydrous aluminum sulfate, Al2(SO4)3, is a specialty item used in food applications. Over 50 acidic, basic, and neutral aluminum sulfate hydrates have been reported. Commercial dry alum is likely not a single crystalline hydrate, but rather it contains significant amounts of amorphous material. In the United States, aluminum sulfate is usually produced by the reaction of bauxite or clay with sulfuric acid. Unfortunately, the term alum is now used for several different materials. Papermakers' alum or simply alum refers to commercial aluminum sulfate. Common alum or ordinary alum usually refers to potash alum which can be written in the form\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{K}}{_{2}}{\rm{SO}} _{4}{\rm{{\cdot{}}}}{\rm{Al}} _{2}{(}{\rm{SO}} _{4}{)}_{3} {\rm{{\cdot{}}}}24{\rm{H}}{_{2}}{\rm{O}}}$\end{document}, or it can refer to ammonium alum, ammonium aluminum sulfate. The term is also applied to a whole series of crystallized double sulfates having the same crystal structure as the common alums. Some examples of alums are cesium alum,\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{CsAl}}{(}{\rm{SO}}{_{4}}{)}_{2}{\rm{{\cdot{}}}}12{\rm{H}}{_{2}}{\rm{O}}}$\end{document}; iron alum,\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{KFe}}{(}{\rm{SO}}{_{4}}{)}_{2}{\rm{{\cdot{}}}}12{\rm{H}}{_{2}}{\rm{O}}}$\end{document}; chrome alum,\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{KCr}}{(}{\rm{SO}}{_{4}}{)}_{2}{\rm{{\cdot{}}}}12{\rm{H}}{_{2}}{\rm{O}}>}$\end{document}; and chromoselenic alum\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{KCr}}{(}{\rm{SeO}}{_{4}}{)}_{2}{\rm{{\cdot{}}}}12{\rm{H}}{_{2}}{\rm{O}}}$\end{document}. In industrial practice it is generally the aluminum content of alums that is important. Because aluminum sulfate is widely available, other alums are more in the nature of specialty items.
Fluorine Compounds, Inorganic, Aluminum
Authors: Meshri Dayal T.
Published: August 2004

Both the binary and complex fluorides of aluminum have played a significant role in the aluminum industry. Aluminum trifluoride trihydrate is of primary importance to the manufacture of aluminum as is sodium hexafluoroaluminate, known as cryolite. Anhydrous aluminum fluoride is used in fluoride glass manufacture and in ceramics. Mixtures of potassium tetrafluoroaluminate and potassium hexafluoroaluminate have been employed as brazing fluxes in the manufacture of aluminum parts. The properties, manufacture, and uses of the various aluminum fluoride compounds are described.
Amine Oxides
Authors: Maisonneuve B.
Published: August 2004

Amine oxides, known asN‐oxides of tertiary amines, are classified as aromatic or aliphatic, depending on whether the nitrogen is part of an aromatic ring system or not. This structural difference accounts for the difference in chemical and physical properties between the two types. The higher aliphatic amine oxides are commercially important because of their surfactant properties and are used extensively in detergents. Amine oxides that have surface‐acting properties can be further categorized as nonionic surfactants; however, because under acidic conditions they show cationic properties, they have also been called cationic surfactants. Most amine oxides undergo thermal decomposition between 90 and 200°C. Aromatic amine oxides, have some pharmaceutical importance, do not demonstrate surface‐acting properties and are more resistant than aliphatic amine oxides to reduction. Linear alpha‐olefins are the source of the largest volume of aliphatic amine oxides. Fatty alcohols and fatty acids are also used to produce amine oxides. Amine oxides used in industry are prepared by oxidation of tertiary amines with hydrogen peroxide solution. Amine oxides are used in the detergent, organic synthesis, textile, and pharmaceutical industries. Aliphatic amine oxides range from practically nontoxic to slightly toxic. Among the aromatics, 4‐nitroquinolineN‐oxide is a powerful carcinogen, producing malignant tumors on the skin of mice. 2‐Methyl, 2‐ethyl, and 6‐chloro derivatives of 4‐nitroquinoline oxide are also carcinogens.
Amino Resins and Plastics
Authors: Williams Laurence L.
Published: August 2004

Amino resins are thermosetting polymers made by combining an aldehyde with a compound containing an amino (\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\relbar \kern-5pt{\relbar}\kern-7pt{\relbar}}{\rm{NH}}{_{2}}}$\end{document}) group. Urea–formaldehyde (U/F) accounts for over 80% of amino resins; melamine–formaldehyde accounts for most of the rest. The principal attractions of amino resins and plastics are water solubility before curing; colorlessness; excellent solvent resistance; outstanding hardness and abrasion resistance; and good heat resistance. Amino resins provide a wide variety of useful products. Adhesives, the largest single market, are used to make plywood, chipboard, and sawdust board. Other types are used to make laminated wood beams, parquet flooring, and for furniture assembly. Aminoplasts and other thermosetting plastics are molded by an automatic injection‐molding process similar to that used for thermoplastics. The process is best applied to relatively small moldings. The great advantage of injection molding is that it eliminates manual labor costs, thereby allowing amino resins to better compete with thermoplastics. The future for amino resins and plastics seems secure. New developments will probably be in the areas of highly specialized materials for treating textiles, paper, etc, and for use with other resins in the formulation of surface coatings. Most amino resins are based on the reaction of formaldehyde with urea or melamine. The first step in the formation of resins and plastics from formaldehyde and amino compounds is the addition of formaldehyde to introduce the hydroxymethyl group, known as methylolation or hydroxymethylation. The second step is a condensation reaction that involves the linking together of monomer units with the liberation of water to form a dimer, a polymer chain, or a vast network, usually referred to as methylene bridge formation, polymerization, resinification, or simply cure. Precise control of the course, speed, and extent of the reaction is essential for successful manufacture. Amino resins are usually made by a batch process. Both urea– and melamine–formaldehyde resins are of low toxicity. Melamine–formaldehyde resins may be used in paper which contacts aqueous and fatty foods. However, some mills are looking for alternatives.
Antiobesity Drugs
Authors: Tilley Jefferson W.
Published: August 2004

Obesity is a difficult condition to treat. Appetite suppressants have been widely used as an adjunct to dietary restriction and sympathomimetic amines have traditionally been used for this purpose. These agents have not proven particularly useful and frequently cause unacceptable side effects; hence their popularity has been waning. The most promising newer drugs work through a serotoninergic mechanism and hold considerable promise at least for certain obese patients. The majority of formerly obese patients eventually regain excess weight lost and thus a truly successful program must include behavior modification. In the central nervous system, sympathetic nervous stimulation results in increases in wakefulness, psychomotor activity, and reduction of appetite. Compounds structurally related to the endogenous sympathomimetic amines norepinephrine and epinephrine have classically been employed as appetite suppressants. These compounds act primarily by indirect mechanism involving displacement of norepinephrine from presynaptic nerve storage vesicles rather than by a direct effect at the receptor level. Whereas they vary in degree, all of them share similar liabilities of cardiovascular side effects, the potential for central nervous system (CNS) stimulation, the development of tolerance, and abuse potential. All, with the exception of mazindol, are derivatives of phenethylamine. Following the Federal Controlled Drug Act of 1970, compounds available in the United States were classified into one of five schedules according to medical utility and abuse potential. They include Schedule II, eg, amphetamine sulfate (C9H14SO4N, Benzedrine) and dextroamphetamine sulfate (C9H14NO4S, Dexedrine); Schedule III, eg, phendimetrazine tartrate (C16H23NO7, Plegine); and Schedule IV, eg, phenteramine hydrochloride (C10H16NCl, Fastin, Adipex‐P, Ionamin). Only drugs in Schedules III and IV are commonly employed for obesity and of them, phenylpropanolamine is available over the counter. Serotoninergic neurons utilize serotonin, C10H12N2O, which is 5‐hydroxytryptamine (5‐HT), as a neurotransmitter. Central serotoninergic neurons play an important role in determining mood and food intake. Fluoxetine (C17H19ClF3NO, Prozac) is a serotonin reuptake inhibitor, is marketed by Eli Lilly as an antidepressant. It was observed in animal studies that fluoxetine decreased meal size and promoted weight loss, and these findings have been extended to humans in clinical trials. Other drugs include gut hormones, lipid adsorption inhibitors, and thermogenic agents.
Ascorbic Acid
Authors: Kuellmer Volker
Published: August 2004

Vitamin C was the first vitamin to be manufactured by chemical synthesis on an industrial scale, and today more vitamin C is produced than any other vitamin. Major suppliers of vitamin C are Hoffmann‐La Roche, BASF, Takeda, and Merck‐Darmstadt. Additional production occurs in Eastern Europe, India, and China. Most of the current industrial production is based on the efficient second synthesis developed by Reichstein and Grüssner in 1934. Various attempts to develop a superior, more economicalL‐ascorbic acid process have been reported since 1934. Much time and effort has been developed to find other methods of vitamin C synthesis by fermentation. The use of the fermentation process for the cost‐effective production ofL‐ascorbic acid, however, requires further improvement.

Both epidemiological and biochemical studies indicate that vitamin C may play an important role in the prevention of cancer, cataracts, and other disorders. However, there are many gaps in the knowledge of vitamin C, eg, in its role in nutritional interrelationships and in metabolic interactions, as well as its role in prevention of various diseases in humans.

Although much additional knowledge concerning the various factors affecting the ascorbic acid status of humans has been acquired in the past decade, the optimum ascorbic acid intake necessary to maintain peak physical and mental health still needs to be established.
Beer
Authors: Nissen J. F.
Published: August 2004

Beer is generally defined as an alcoholic beverage made by fermentation of a farinaceous extract that is obtained from a starchy raw material, barley, in the form of malt. Although it is possible to replace some part of the barley with other starchy materials (eg, corn, rice, wheat, oats, or potatoes), it is usually the main constituent of brewing materials. There are many production steps in the brewing of beer, involving some of the most difficult disciplines of biochemical and physical science. Despite the scientific knowledge developed in the last century, some brewing information remains culturally derived. Conditions such as tradition, taxation, and other peculiarities have resulted in a beer market characterized by numerous types varying in strength, color, alcohol content, and bitterness.
Butadiene
Authors: Sun H. N. , Wristers J. P.
Published: August 2004

Butadiene, C4H6, exists in two isomeric forms: 1,3‐butadiene\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{CH}}{_{2}}{\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}} {\rm{CH}}{\relbar \kern-5pt{\relbar}\kern-7pt{\relbar}}{\rm{CH}}{\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}} {\rm{CH}}{_{2}}}$\end{document}, and 1,2‐butadiene,\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{CH}}{_{2}}{\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}} {\rm{C}}{\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}}{\rm{CH}}{\relbar \kern-5pt{\relbar}\kern-7pt{\relbar}}{\rm{C}}{_{3}}}$\end{document}. 1,3‐Butadiene is a commodity product of the petrochemical industry. Elastomers consume the bulk of 1,3‐butadiene, led by the manufacture of styrene–butadiene rubber (SBR). 1,3‐Butadiene is manufactured primarily as a coproduct of steam cracking to produce ethylene in the United States, Western Europe, and Japan. However, in certain parts of the world, eg, China, India, Poland, and the former Soviet Union, it is still produced from ethanol. The other isomer, 1,2‐butadiene, has no significant current commercial interests. 1,3‐Butadiene is a noncorrosive, colorless, flammable gas at room temperature and atmospheric pressure. It has a mildly aromatic odor. It is sparingly soluble in water, slightly soluble in methanol and ethanol, and soluble in organic solvents like diethyl ether, benzene, and carbon tetrachloride. The conjugated double bonds of 1,3‐butadiene allow a large number of reactions at both the 1,2‐ and 1,4‐positions. These reactions include addition, hydrogenation, oxidation, Diels‐Alder, oligomerization, and polymerization reactions. Many of these reactions produce large volumes of important industrial materials. Butadiene reacts with a large number of chemicals, has an inherent tendency to dimerize and polymerize, and is toxic. Therefore, specific handling, storage, and shipping procedures must be followed. U.S. shipments of butadiene, which is classified as a flammable compressed gas, are regulated by the Department of Transportation. Short‐term exposure to high concentrations of butadiene may cause irritation to the eyes, nose, and throat. Dermatitis and frostbite may result from exposure to the liquid and the evaporating gas. In several epidemiological studies, elevation in mortality was observed for small subgroups and tumor types. Interpretation of these findings is still incomplete.
Cadmium Compounds
Authors: Herron Norman
Published: August 2004

Naturally occurring cadmium compounds are limited to the rare minerals, greenockite, CdS, and otavite, an oxycarbonate, but neither is an economically important source of cadmium metal or its compounds. Instead, cadmium compounds are usually derived from metallic cadmium produced as a by‐product of lead‐zinc smelting or electrolysis. In general, cadmium compounds exhibit properties similar to the corresponding zinc compounds. The principal areas of cadmium usage in terms of U.S. consumption in 1990 were batteries, 50%; pigments, 20%; plastic stabilizers, 15%; metal finishing, 10%; electronics and optics,

\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{<}}5{\%}}$\end{document}

; and catalysts,

\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{<}}5{\%}}$\end{document}

. Cadmium hydroxide is the anode material of Ag–Cd and Ni–Cd rechargeable storage batteries. Cadmium sulfide, selenide, and especially telluride find utility in solar cells. In flexible PVC, cadmium salts such as stearate are used as heat and light stabilizers. Cadmium cyanide, acetate, fluoroborate, or sulfate is used as an electrolyte in electroplating onto other metals, imparting corrosion protection. The cadmium chalcogenide semiconductors have found numerous applications ranging from rectifiers to photoconductive detectors in smoke alarms. Many Cd compounds are used as phosphors in luminescent screens. Demand for cadmium and its compounds in the United States has generally declined after peaking during the late 1970s. The declining use of cadmium in plastics and as pigments in the 1980s, largely because of health and environmental concerns and the concomitant introduction of Cd substitutes, has been offset by its increased use in rechargeable storage (Ni–Cd) batteries. Continued and growing concern over the toxicity of cadmium in the environment is expected to lead to alternatives for cadmium compounds in all applications. Inorganic compounds include cadmium arsenides, antimonides, and phosphides; cadmium borates; cadmium carbonate; cadmium complexes; cadmium halides; cadmium hydroxide; cadmium nitrate; cadmium oxide; cadmium phosphates; and others. Many organocadmium compounds are known but few have been of commercial importance. They include dialkyl cadmium compounds, cadmium acetate, and organocadmium soaps.
Aluminum Oxide (Alumina), Calcined, Tabular, and Aluminate Cements
Authors: MacZura George
Published: August 2004

Calcined aluminas are generally obtained from Bayer process gibbsite α‐Al(OH)3, thermal decomposition of which follows the transition through the generic gamma alumina phases to α‐alumina (corundum), α‐Al2O3. Calcination of gibbsite has been done in rotary kilns for many years. Specialty calcined aluminas can also be prepared in stationary or fluid bed calciners. Most ceramic grade aluminas are supplied dry ground to about 95%\documentclass{article}\pagestyle{empty}\begin{document}${{\rm{-}}325{\hskip0.167em}{\hskip0.167em}{\rm{mesh}}}$\end{document}(44 µm) using 85–90% Al2O3ceramic ball, attrition, vibro‐energy, or fluid‐energy milling. More fully ground, or superground, calcined aluminas having particle size distributions that approximate the natural or ultimate crystal size of the Bayer grain as calcined are often desired. Thermally reactive aluminas contain submicrometer crystals. These must be separated from the Bayer agglomerate during grinding to permit dense compaction upon ceramic forming, and thus, enhance densification upon sintering at lower temperatures. Process control techniques permit production of calcined specialty aluminas having controlled median particle sizes differentiated by about 0.5 µm. This broad selection enables closer shrinkage control of high tech ceramic parts. Tabular alumina is a high density, high strength form of α‐Al2O3made by sintering an agglomerated shape of ground, calcined alumina. It is available in the form of smooth balls which are crushed, screened, and ground to obtain a wide variety of graded, granular, and powdered products. Tabular alumina is the ideal base material for high alumina brick, and monolith liners in the metal, ceramic, and petrochemical industries. Other applications include their use in electrical insulators, electronic components, and kiln furniture. High purity calcium aluminate cements (CAC) are primarily used as binders for high strength refractory castables to form linings up to about 1.0 m thick, as in iron blast furnaces. The high purity CAC finds extensive use as an efficient binder for other aggregates such as fire clays, kaolin, andalusite, kyanite, pyrophyllite, sillimanite, mullite, and refractory‐grade bauxite. The many applications cited for tabular alumina in refractories are also common for high purity CAC.
Calcium Sulfate
Authors: Petersen Donald J. , Kaleta Norbert W. , Kingston Larry W.
Published: August 2004

Calcium sulfate, CaSO4, in mineral form is commonly called and occurs abundantly in many areas of the world. In natural deposits, the main form is the dihydrate. Some anhydrite is also present in most areas, although to a lesser extent. The hemihydrate is normally produced by heat conversion of the dihydrate. The resulting powder is also known as plaster of Paris. Stucco has the greatest commercial significance of these materials. It is the primary constituent used to fabricate products and in formulated plasters used in job or shop‐site applications. About\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${23\times 10^{6}{\hskip0.167em}{\hskip0.167em}{\rm{t}}}$\end{document}of gypsum are consumed annually. About 80% is processed into the commercially usable hemihydrate. Uses of gypsum are in fabricated or formulated building materials, Portland cement set regulation, and agricultural soil conditioning. The natural, or mineral, form of gypsum is most widely extracted by mining or quarrying and used commercially. Gypsum is also obtained as a by‐product of various chemical processes. The main sources are from processes involving scrubbing gases evolved in burning fuels that contain sulfur, and the chemical synthesis of chemicals, such as sulfuric acid, phosphoric acid, titanium dioxide, citric acid, and organic polymers. Gypsum rock from the mine or quarry is crushed and sized to meet the requirements of future processing or removed for direct marketing of the dihydrate as a cement retarder. Once subjected to a secondary crusher, calcining, and drying, the product is fine‐ground. The majority of fine‐ground dihydrate is used as feed to calcination processes for conversion to hemihydrate. The dehydration of gypsum, commonly referred to as calcination in the gypsum industry, is used to prepare hemihydrate, or anhydrite. Three processing methods are used for the production of α‐hemihydrate. One involves charging lump gypsum rock into a vertical retort and applying steam. After calcination for 5–7 h the hot moist rock is quickly dried and pulverized. Another method has lower water demand. The dihydrate is heated in a water solution containing a metallic salt at pressures not exceeding atmospheric. A third method prepares very low water‐demand α‐hemihydrate by auto‐claving powdered gypsum in a slurry. A crystal‐modifying substance is added to produce large squat crystals. Soluble anhydrite is commercially manufactured in a variety of forms by low temperature dehydration of gypsum. Crude gypsum is the principal form of calcium sulfate shipped in international trade, although by the 1980s an increased volume of fabricated products moved across international borders.
Carbon Disulfide
Authors: Smith David E. , Timmerman Robert W.
Published: August 2004

Carbon disulfide, CS2, is a highly volatile, flammable, clear, colorless, dense liquid that has many useful chemical and physical properties. An industrially important chemical for over one hundred years, most carbon disulfide is now produced by reaction of hydrocarbon gas with sulfur in a process developed in the 1950s, although many small capacity plants still employ a retort or electric furnace route based on wood charcoal and sulfur. Modern plants achieve a 99.99% pure carbon disulfide product by means of fractional distillation. Over 75% of the estimated one million tons of carbon disulfide produced worldwide in 1991 went into manufacturing viscose rayon and cellophane film. Carbon disulfide is also used in manufacturing numerous organic sulfur compounds for a variety of applications including rubber vulcanization accelerators, flotation chemicals, pharmaceutical intermediates, fungicides, and insecticides. The carbon disulfide process route to carbon tetrachloride was discontinued in the United States during 1991 because of environment pressures on the end product. Carbon disulfide is very toxic, and the U.S. Government limits the 8‐h time‐weighted average exposure to 4 ppm maximum (12 mg/m3) in air. Health and environmental concerns related to carbon disulfide have curtailed some uses, such as in grain fumigants and solvents. Special precautions must be exercised in handling carbon disulfide because of its toxicity, high volatility, wide flammability range, and low ignition temperature.
Cardiovascular Agents
Authors: Cervoni Peter , Crandall David L. , Chan Peter S.
Published: August 2004

The six primary classes of cardiovascular drugs, ie, antiarrhythmic agents, antianginal agents, agents used in the treatment of congestive heart failure, antiatherosclerotic agents, antihypertensive agents, and thrombolytic agents, are reviewed. An overview of the physiology of the cardiovascular system is presented for each class together with the pathology of the system leading to specific cardiovascular disorders. The mechanism(s) of action of the cardiovascular agents are discussed when known, and the principal actions of the cardiovascular agents that contribute to amelioration of the underlying pathology of the cardiovascular disease are reviewed. Side effects and toxicities of the cardiovascular agents are also presented. Drugs clinically in use and some of those drugs under development are discussed. A brief review of the current and projected sales of ethical pharmaceuticals is presented in relation to the sales of cardiovascular agents which is the fastest growing segment of the ethical pharmaceutical market.
Catalysis
Authors: Gates Bruce C.
Published: August 2004

Catalysis is the key to efficient chemical processing. Catalysts increase the rates of chemical reactions without affecting the equilibrium and, ideally, without being consumed. Catalysts work by forming chemical bonds with reactants and providing energetically favorable pathways for their conversion into products. This article is a summary of catalysis in solutions and on surfaces, including basic definitions and principles and numerous industrial examples; it is organized to emphasize the unity of the subject, direct the reader to the literature, and provide practical guidelines about technological applications.
Separation, Centrifugal Separation
Authors: Letki Alan , Moll R. T. , Shapiro Leonard
Published: August 2004

Separation by density difference and drainage is presented, along with formulas developed for bottle, solid wall, and disk centrifuges. The Σ‐concept is developed and several practical variants are discussed. Liquid–liquid separation interface location formulas are reviewed. Centrifuge components, including a breakdown of power and energy losses with applicable information for centrifuges, are represented. Centrifuge materials of construction and their corrosion, erosion, and strength characteristics are reviewed. Stresses generated owing to rotation and material and process fluids, abrasion resistance, and noise generated by centrifuges are discussed. The various types of sedimentation and filtration equipment are reviewed. Examples of use, rates, and performance of bottle; disk; continuous conveyor discharge; preparation; zonal; tubular; perforate basket; inverting filter; conical; and continuous single‐ and multiple‐stage pusher centrifuges are reviewed. Gas centrifuges and their use in uranium enrichment are presented.
Ceramics As Electrical Materials
Authors: Buchanan R. C. , Roseman R. D.
Published: August 2004

There are a large number of applications for ceramic materials where electrical conduction properties are important. These materials exhibit a wide range of conductivities from highly insulating to highly conducting. Other electrical properties, associated with magnetic and dielectric polarization, superconduction, and environmental sensing functions, may also be present. Ceramic properties are developed through composition selection combined with highly specific firing or heat treatment processes, where the base compositions and dopants interact to give complex materials having engineered micro and defect structures. Many of the developed ceramics are an integral part of modern microcircuit technology, in which advantage is taken not only of the high resistivity and range of dielectric behavior, but of the semiconducting and low resistivity properties. The development of electronic components, such as highly complex sensors and actuators, superconductors, multilayer and miniaturized microelectronic devices, and insulation applications for high frequency, temperature, voltage, and stressed components, have been made possible through the use of these ceramics. The conduction phenomena and mechanisms that control electrical behavior in each type of material is discussed.
Chelating Agents
Authors: Howard William L. , Wilson David A.
Published: August 2004

Chelating agents or chelants are compounds having two or more donor atoms that can form cyclic coordination complexes or chelates with acceptor metals. The complexation is an equilibrium reaction which often strongly favors the complex. Chelating is used to modify or control the behavior of metals and their compounds by controlling the concentration of the metals in solution or to utilize the special properties of the chelation compounds. The active groups in chelants may be linear chains, eg, ‐N‐C‐C‐N‐, macrocyclic rings, eg [‐O‐C‐C]n, or polycyclic structures, such as the cryptates, eg, X[‐C‐C‐Y‐C‐C)n]3Y where X and Y are bridgehead and donor atoms, respectively. Some pH, stability, solubility, and electrochemical relationships among simultaneous equilibria in chelation are shown. A broad range of applications based on concentration control, the special properties, and medical uses of chelation compounds are given. Metal sequestration, solubilization, and buffering are discussed as are metal extraction, precipitation, and displacement. Economic data for industrial chelating agents are given. Use of chelating agents is essentially benign environmentally and presents little or no hazard to health or safety under normal conditions of use and handling.
Chemicals In War
Authors: Harris B. L.
Published: August 2004

Chemicals used in war fit into five categories: flame agents, incendiaries, smokes and obscurants, incapacitants and riot control agents, and toxic agents. Flame agents, typically hydrocarbons or other readily flammable liquids, are used in flame throwers and flame projectors such as flame rockets. Incendiaries are often metals such as magnesium or aluminum, or oil and metal mixtures. These materials often require a fuse or ignition cup. Smokes and obscurants may be gaseous, liquid, or particulate aerosols. Incapacitants and riot control agents are designed to incapacitate but not permanently damage. These substances may be atropinemetics, or lacrimators, sternutators, vesicants, or urticants. Effects of atropinemetics may last from a few hours to a few days; effects of the latter materials usually dissipate within minutes upon removal from the agent. The toxic agents are generally of two types, vesicants such as the sulfur or nitrogen mustard gases, or the organophosphate nerve agents.

Defense against toxic agents requires agent detection and identification; individual and collective protection of personnel and equipment; decontamination materials and procedures; and medical defense.
Chlorine Oxygen Acids and Salts, Chloric Acid and Chlorates
Authors: Mendiratta Sudhir K. , Duncan Budd L.
Published: August 2004

Sodium chlorate is the primary raw material for the manufacture of chlorine dioxide, a bleaching agent in the pulp and paper industry. Increases in the chlorine dioxide substitution for chlorine in pulp bleaching have resulted in an average growth of 12%/y in production. Sodium chlorate is prepared electrolytically. The modern technology described minimizes sodium chloride and sodium dichromate impurities. Chlorates are powerful oxidizers, and they are also used in perchloric salt and uranium production.

Chloric acid technologies have been developed which allow the generation of chlorine dioxide directly from the acid, without the formation of sodium salts in the generator.
Chloramines and Bromamines
Authors: Wojtowicz John A.
Published: August 2004

N‐Halamines are inorganic and organic compounds in which halogen is attached to nitrogen. They have both research and commercial importance. TheN‐halogen bond is formed by reaction of an amine, imine, amide, or imide with halogen, hypohalous acid, or hypochlorite. Only the chloro and bromo derivatives are of commercial importance. The physical and chemical properties, preparation, manufacture, uses, safety and handling, toxicity, and economic aspects of chloramines and bromamines are discussed. The chemistry of chloramines and bromamines is diversified not only because nitrogen and halogen act as reaction sites but because of the different modes by which these functionalities react. Research activity on synthetic applications of chloramines and bromamines continues to be high.

In aqueous solution, these chloramines and bromamines undergo hydrolysis to varying degrees forming hypochlorous and hypobromous acids. Thus theseN‐halamines can be considered as halogen release agents and many, eg, chloroisocyanurates, find use in bleaching, disinfecting, and sanitizing applications. Others, such as halogen derivatives of ammonia, are important because they are industrial process intermediates (monochloramine) or of significance in water treatment (mono‐, di‐, and trichloramine).
Chromium and Chromium Alloys
Authors: Westbrook Jack H.
Published: August 2004

Chromium metal, chromium alloys, and metallurgically important chromium compounds are reviewed. Occurrence, mining, and smelting of chromium ores are discussed. The chemical, physical, and mechanical properties of chromium metal are summarized. Important Cr‐bearing alloys: the various stainless steels, alloy steels, nonferrous alloys, and Cr‐based alloys are identified as are metallurgically important compounds. Applications of these materials are discussed and the contribution of chromium to the properties of these alloys is described. Methods of producing Cr‐rich protective and decorative surfaces, recovery and reuse of Cr‐bearing materials, and toxicology are reviewed.
Coal
Authors: Vorres Karl S.
Published: August 2004

Coal.Coal, mined throughout the world, is used primarily for electric power generation in the United States either as the solitary fuel or in cogeneration systems. Steelmaking is the second largest usage for coal. The constituent original plant parts can be identified microscopically and coal is classified according to heating value, fixed carbon, and coking properties. Classes of coal range from the hard anthracite to the soft subbituminous materials and lignite. Sulfur in coal may be in both organic and inorganic constituents. The inorganic sulfur is more easily removed. Coal properties are tied to composition and to structure.

Synthetic crude oil can be produced from coal by hydrogenation, and transportation fuels by indirect liquefaction or gasification. Gasifiers are used to make chemical intermediates and to produce electric power by integrated gasification combined cycle systems. Coal cleaning is important to meeting environmental regulations. Coal reserves in the United States can sustain U.S. demand for over 100 years.
Cobalt and Cobalt Alloys
Authors: Hodge F. Galen
Published: August 2004

Cobalt is a metallic element the earliest uses of which were as colorants for glass and pottery. Cobalt has unique magnetic properties. The largest consumption of cobalt is in the metallic form as magnetic alloys, cutting and wear‐resistant alloys, and high temperature superalloys. The second largest use of cobalt is in the form of salts, including lacquers, enamels, colorants for glass, and catalysts. Radioactive cobalt has considerable application in radiochemistry and radiography.

Cobalt‐base alloys are generally described as wear‐resistant, corrosion‐resistant, and heat‐resistant. Many of the properties of the alloys arise from the crystallographic nature of cobalt, the solid solution strengthening effects of chromium, tungsten, and molybdenum, the formation of carbides, and the corrosion resistance imparted by chromium.
Cobalt Compounds
Authors: Richardson H. Wayne
Published: August 2004

An overview of cobalt compounds including the chemistry exhibited by the +2 and +3 valences is presented emphasizing those compounds of industrial significance. Methods of manufacture for many of the commercial compounds are given as is transition‐metal separation methodology. The biological role of cobalt in humans and ruminants is discussed.

The primary use of cobalt compounds is in catalysis for hydrotreating petroleum resulting in hydrodesulfurization. Cobalt catalysts are also used to denitrify, deoxgenate, crack crude oil and gas, and in homogeneous oxidation and the oxo process (hydroformylation). Cobalt compounds are used in pigments for paints and priting iks, as colorants for glass, ceramics, and enamels, and in the form of metallic soaps as driers. Less significant industrial uses are in electronics, agriculture as feed and soil additives, and as an adhesive in the tire industry.
Color Photography
Authors: Kapecki Jon , Rodgers James
Published: August 2004

Color photography is the technology by which the visual appearance of a three‐dimensional subject may be reproduced on a two‐dimensional surface having a pleasing balance of brightness, hue, and color. Light capture is primarily effected by silver halide crystals. Integral tri‐color film packs also contain spectral sensitizing dyes and colored masking couplers appropriate to the subtractive primary dyes, filters, and an overcoat.

The chromogenic chemistry of the color photography process involves the reactions ofp‐phenylenediamine developers and various couplers. Prototype dye couplers, which often contain an organic ballast to enhance solubility in hydrophobic solvents, colored masking couplers, and development‐inhibitor‐releasing couplers, which carry a silver development inhibitor linked to the film coupling site, are given. Both chromogenic and post‐development film chemistries are described as are the relationships between film speed, light sensitivity, dye stability, image structure, and color reproduction.
Helium Group Compounds
Authors: Schrobilgen Gary J. , Whalen J. Marc
Published: August 2004

Compounds of the helium‐group gases, known since 1962, are limited to those of xenon, krypton, and radon. These heavy noble gases form stable compounds and adducts with fluorine and other powerful oxidants. Xenon has the best studied, most extensive chemistry. The oxidation states observed for xenon range from\documentclass{article}\pagestyle{empty}\begin{document}${+}$\end{document}to\documentclass{article}\pagestyle{empty}\begin{document}${+8}$\end{document}. Bonds to fluorine, oxygen, nitrogen, and carbon have been characterized. The chemistry of krypton, which has one known oxidation state,\documentclass{article}\pagestyle{empty}\begin{document}${+2}$\end{document}, is far less extensive, but bonds to fluorine, oxygen, and nitrogen have been characterized. That of radon is even less well characterized and is limited to fluoride species of the\documentclass{article}\pagestyle{empty}\begin{document}${+2}$\end{document}oxidation state. Properties of the compounds are reviewed.
Copper
Authors: George David B.
Published: August 2004

Copper and its various alloys are used in industrial and consumer applications because of high electrical and thermal conductivities, wear and corrosion resistance, and mechanical and aesthetic properties. These metals are vital to nearly every industrial sector. Uses of copper and alloy mill products may be broken down into five principal markets: building construction, electrical and electronic products, industrial machinery and equipment, transportation, and consumer and general products. In addition, copper and its alloys are a strategic material essential to the production of equipment critical to the U.S. economy and national defense.

The various copper minerals, mining, ore treatment, smelting, and refining are discussed as is fabrication of products and the chemical reactions specific to these processes. There have been significant process innovations in the copper industry, particularly in hydrometallurgy, solvent‐extraction technology, and continuous casting production methods.

Pure copper is most often produced by electromining. Sulfuric acid is a principal by‐product of copper refining. The United States is a world leader in smelting and refining capacity. It is the second largest copper ore producer and repository of one‐fifth of the world's recoverable reserves. U.S. and world production is discussed.
Copper Compounds
Authors: Wayne Richardson H.
Published: August 2004

An overview of copper compounds is presented with the emphasis on those compounds of key industrial importance. The chemistry and stability of copper in its various oxidation states and with regard to coordination complexes are discussed. The primary methods of manufacture for many commercially significant compounds are given as are the most usual methods of analysis. The uses of copper in agriculture, as a nutritional fungicide and algicide are discussed. The various copper‐bond fungicides are listed. Other uses of copper compounds such as in catalysis, electronics, and electroplating are mentioned. Copper compounds are also used as pigments, in wood preservation and electroless plating, and in solar collectors.
Cyanamides
Authors: Patel Baldev K.
Published: August 2004

Cyanamide has been commercially available, as calcium salt, since the beginning of the twentieth century. A commercial process for manufacturing a pure grade of cyanamide was introduced in 1964. Cyanamide was widely used as a nitrogen fertilizer and later as a raw material for dicyandiamide and melamine.

The use of cyanamide as a fertilizer has been replaced by ammonia and urea. Melamine is now made by a petrochemical process using natural gas. Cyanamide is still used in the manufacture of dicyandiamide and calcium cyanide. Cyanamide‐based chemicals have also been used in special applications for defoliants, fungicides, herbicides, and as a weed killer. In pure form, cyanamides are used in the synthesis of many complex chemicals.

Calcium cyanamide is produced by both batch oven and continuous kiln processes. This article deals with the chemistry, manufacture, specifications, health and safety factors (toxicity and environment), and use of cyanamide homologues: cyanamide, dicyandiamide, and melamine.
Cyanuric and Isocyanuric Acids
Authors: Wojtowicz J. A.
Published: August 2004

Cyanuric acid has been known for over 200 years, but achieved commercial importance only in the mid‐1950s primarily via its derivatives. The chemistry of cyanuric acid is diversified because of multiple reaction sites.N‐Chlorination of cyanuric acid produces chloroisocyanurates that are widely used as disinfectants, sanitizers, and bleaches. The triallyl‐ and tris(2‐hydroxyethyl) derivatives are employed as cross‐linking and curing agents, and tris(2,3‐epoxypropyl)isocyanurate is used in weather‐resistant powder coatings. Melamine cyanurate finds significant use as a fire retardant in plastics. Considerable interest has developed in the use of cyanuric acid for reduction of nitrogen oxides in exhaust gases from combustion of oil, gas, and coal.

Nomenclature is based on the keto‐enol tautomers. The trihydroxy form is variously designated cyanuric acid,s‐triazine‐2,4,6‐triol or 2,4,6‐trihydroxy‐s‐triazine. The trioxo structure, ors‐triazine‐2,4,6(1H,3H,5H)‐trione is the basis for the isocyanuric acid nomenclature. The triazine‐based system is preferred in the scientific literature and is used by government regulatory agencies; however, the less cumbersome (iso)cyanurate designations persist in commerce. The keto form normally predominates in cases of keto‐enol tautomerism. In alkaline solution, the anion formed is that of the hydroxy tautomer. Through common usage, both forms are collectively called cyanuric acid (CA).
Defoamers
Authors: Owen Michael J.
Published: August 2004

Modern defoamers are complex formulated products of vital importance in a wide variety of industries. A classification by chemical type is presented based on active liquid and solid phase components and ancillary surface‐active materials and carriers. Traditional vegetable and mineral oils, poly(oxypropylene), polydimethylsiloxane, alkyl phosphates, acetylenic glycols, hydrophobic silica, and solid fatty amides are included together with examples of commercial sources. Current theory of defoaming is reviewed from the perspective of the spreading properties of liquid‐phase components and the dewetting of foam films from the solid‐phase components. Emphasis is on surface dilatational properties, using silicone defoaming of crude oils as an example, and on the role of the dispersed hydrophobic solids in aqueous defoaming, using hydrophobic silica as the example. The principal industries and application areas where defoamer use is most critical are reviewed including adhesives and sealants, chemical processing, cleaning compounds, construction, fermentation, fertilizers, food and beverages, leather, metal working, oil and petroleum, paints and coatings, polymers, pulp and paper, textiles, and wastewater treatment. Economic aspects, test methods, and health and safety factors are also briefly covered.
Dental Materials
Authors: Tesk John A. , Antonucci Joseph M. , Eichmiller Fred C. , Kelly J. Robert , Rupp Nelson W. , Waterstrat Richard W. , Fraker Anna C. , Chow Lawrence C. , George Laurie A. , Stansbury Jeffrey W. , Parry Edward E.
Published: August 2004

Dental materials are those materials used to provide therapy for the hard and soft oral tissues. This therapy includes the replacement of oral tissues lost through disease with inert materials, ie, metallic, ceramic, and organic, or with composites employing combinations of these three broad classes. The operative restorations and prostheses are made of amalgam, precious and nonprecious alloys, special cements, synthetic polymers, porcelain, and glass‐ceramics, all of which must withstand the rigors of the oral environment (see also Prosthetic and Biomedical Devices). The accessory materials needed in the fabrication procedures include synthetic polymers, synthetic and natural gums and waxes, hydrocolloids, gypsums, and refractories.

These materials are used by ca 170,000 practicing dentists in the United States (1992) and more than 8,500 commercial U.S. dental laboratories employing ca 40,000–50,000 technicians.
Deuterium and Tritium, Deuterium
Authors: Katz Joseph J.
Published: August 2004

Deuterium (2H or D) the heavier, stable isotope of hydrogen (1H) occurs in nature, and is always present in all hydrogen‐containing compounds. Deuterium oxide, known as heavy water, is the most important deuterium compound. Heavy water differs from ordinary water in structure of the liquid phase, in nuclear spin, ionic equilibria, and in various spectroscopic properties. Kinetic isotope effects occur in chemical reactions involving bond rupture of H and D. This effect in hydrogen exchange between water and hydrogen sulfide is the basis for the most important separation process for large‐scale deuterium production. Infrared absorption is the method of choice for the analysis of heavy water. Deuterium has far‐reaching biological effects, and it is possible to grow living organisms in which all of the hydrogen normally present is replaced by deuterium. The nuclear properties of deuterium are such that heavy water is the most efficient neutron moderator known for nuclear fission reactors. Deuterium is also important in nuclear fusion technology.
Dispersants
Authors: Hann William M.
Published: August 2004

Dispersants are polymeric compounds that help maintain fine solid particles in suspension in a fluid medium or that inhibit the growth of crystallites in a supersaturated solution. Dispersants function by adsorbing on active sites in a growing crystal or by adsorbing on solid particle surfaces to provide a barrier that prevents particle aggregation. This barrier can be due to coulombic (charge) repulsion, steric repulsion, or both. Significant uses for dispersants include detergent builder assists, water treatment applications, paint and pigment dispersing, and in cements to increase workability. The principal types of dispersants are polyphosphates, polyacrylates, polymaleates, melamine‐ or naphthalene‐sulfonic acid condensates, and natural product‐derived dispersants. In general, dispersants are used to prevent settling, deposition, precipitation, agglomeration, flocculation, coagulation, adherence, or caking of solid particles.