bluuebunny/crossref_metadata_2025 huggingface dataset:
Butadiene
Authors: Sun H. N. , Wristers J. P.
Published: July 2004

Butadiene, C4H6, exists in two isomeric forms: 1,3‐butadiene and 1,2‐butadiene. 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 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. Updated exposure limits are given. Butadiene is used primarly in polymers. Other uses are given.
Butyl Alcohols
Authors: Billig Ernst
Published: July 2004

Butyl alcohols encompass the four structurally isomeric 4‐carbon alcohols of empirical formula C4H10O. One of these, 2‐butanol, can exist in either the optically active R(−) or S(+) configuration or as a racemic (±) mixture. The butanols are all colorless, clear liquids at room temperature and atmospheric pressure with the exception oft‐butyl alcohol which is a low melting solid; it also has a substantially higher water miscibility than the other three alcohols. The butanols undergo the typical reactions of the simple lower chain aliphatic alcohols. The principal commercial source of 1‐butanol isn‐butyraldehyde, obtained from the Oxo reaction of propylene. The largest‐volume commercial derivatives of 1‐butanol aren‐butyl acrylate and methacrylate. These are used principally in emulsion polymers for latex paints, in textile applications and in impact modifiers for rigid poly(vinyl chloride). All four butanols are thought to have a generally low order of human toxicity. The C‐4 alcohols are preferably stored in baked phenolic‐lined steel tanks. However, plain steel tanks can also be employed. Storage under dry nitrogen is also recommended since it limits flammability hazards.
Cadmium and Cadmium Alloys
Authors: Morrow Hugh
Published: July 2004

Cadmium, Cd, a Group 12 (IIB) element occurring between zinc and mercury, is a soft, ductile, silver‐white metal having a distorted hexagonal close‐packed structure. The crustal abundance of cadmium is somewhere between 0.1 and 0.5 ppm, and several cadmium minerals have been identified, the most common being greenockite, CdS. Cadmium is generally encountered in zinc ores, zinc‐bearing lead ores, or complex copper‐lead‐zinc ores, where, however, it forms an isomorphic impurity in the zinc mineral sphalerite, ZnS. For this reason, cadmium is almost invariably recovered as a by‐product from the processing of zinc, lead, and copper ores. Its oxidation state in almost all of its compoumds is + 2, although a few compounds have been reported in which cadmium exists in the + 1 oxidation state. There are eight natural isotopes. Cadmium forms a fume of brown‐colored cadmium oxide, CdO, when heated in air. Other elements which react readily with cadmium metal upon heating include the halogens, phosphorus, selenium, sulfur, and tellurium. Cadmium is rapidly oxidized by hot dilute nitric acid. Cadmium occurs primarily as sulfide minerals in zinc, lead‐zinc, and copper‐lead‐zinc ores. Beneficiation of these minerals, usually by flotation or heavy‐media separation, yields concentrates which are then processed for the recovery of the contained metal values. Cadmium follows the zinc with which it is so closely associated. Air pollution problems and labor costs have led to the closing of older pyrometallurgical plants, and to increased electrolytic production. Cadmium production is dependent on the processing of zinc ores, which often contain 0.2 to 0.4% cadmium. Cadmium is classified as a toxic metal. Acute industrial poisoning by cadmium dust or fume can occur during the melting or pouring of cadmium metal; the welding, burning, or heating of cadmium‐plated steel; or spraying, brazing, and overheating of cadmium metal. Protection should be provided by a properly designed exhaust ventilation system or by a suitable individual filter or air‐supplied respirator. Industrial exposure to cadmium fumes and dust has been reported to result in emphysema, hypertension, kidney failure, osteomalacia, and perhaps an increased incidence of cancer. To help maintain the balance between supply and demand for cadmium, efforts can be made to recycle such cadmium‐containing materials as spent nickel‐cadmium batteries as well as dust and other residues from the pigment industry. Consumption of cadmium is in batteries, coating and plating, pigments, plastics and synthetic products, and alloys and other uses. Cadmium is an important component in brazing and low melting alloys, used in bearings, solders, and nuclear reactor control rods.
Cadmium Compounds
Authors: Herron Norman
Published: July 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 2001 were batteries, 75%; pigments, 12%; coatings and plating, 8%; plastic stabilizers, 4%; and nonferrous alloys and other uses, 1%. 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. 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.
Calcium Carbide
Authors: Cameron William L.
Published: July 2004

Chemically pure calcium carbide, Ca
2
C, is a colorless solid; however, the pure material can be prepared only by very special techniques. China is the world's largest producer of calcium carbide. Commercial calcium carbide is composed of calcium carbide, calcium oxide, CaO, and other impurities present in the raw materials. Industrial‐grade calcium carbide contains about 80% as CaC
2
, 15% CaO, and 5% other impurities. In the United States calcium carbide‐based acetylene is mainly used in the oxyacetylene welding market, although some continues to be used for production of such chemicals as vinyl ethers and acetylenic alcohols. Calcium carbide is used extensively as a desulfurizing reagent in steel and ductile iron production, allowing steel mills to use high sulfur coke. The exothermic reaction of calcium carbide and water‐yielding acetylene forms the basis of the most important industrial use of calcium carbide. An important use of calcium carbide has developed in the iron and steel industries, where the carbide has been found to be an effective desulfurizing agent for blast‐furnace iron. Calcium carbide is produced commercially by reaction of high purity quicklime and a reducing agent such as coke in an electric furnace at 2000–2200°C. Commercial calcium carbide, containing about 80% CaC
2
, is formed in the liquid state. The liquid calcium carbide is tapped from the furnace into cooling molds. Calcium carbide is classed as a hazardous chemical under U.S. Department of Transportation regulations. Domestic shipments are mainly in steel tote bins. Containers must be marked “Flammable solid, dangerous when wet” and have the United Nations designation UN 1402. Although acetylene is considered to be a material having a very low toxicity, a threshold limit value (TLV) of 2500 ppm has been established by NIOSH. In the presence of a small amount of water carbide may become incandescent and ignition of the evolved air–acetylene mixture may occur. Nonsparking tools should be used when working in the area of acetylene‐generating equipment.
Calcium and Calcium Alloys
Authors: Vrana Lisa M.
Published: July 2004

Calcium, Ca, a member of Group 2 (IIA) of the Periodic Table between magnesium and strontium, is classified, together with barium and strontium, as an alkaline‐earth metal and is the lightest of the three. Calcium metal does not occur free in nature; however, in the form of numerous compounds, it is the fifth most abundant element, constituting 3.63% of the earth's crust. Calcium is mainly used for improvement of steel; as a reducing agent for many reactive, less common metals; to remove bismuth from lead; as a desulfurizer and deoxidizer for ferrous metals and alloys; as an alloying agent for aluminum, silicon, and lead in the manufacture of lead–acid batteries and for permanent magnet manufacture. Pure calcium is a bright, silvery‐white metal, although under normal atmospheric conditions, freshly exposed surfaces of calcium quickly become covered with an oxide layer. The metal is extremely soft and ductile. Calcium's usefulness as a structural material is limited by low tensile strength and high chemical reactivity. Calcium has a valence electron configuration of 4
s
2
and characteristically forms divalent compounds. It is very reactive and reacts vigorously with water, liberating hydrogen and forming calcium hydroxide, Ca(OH)
2
. Calcium does not readily oxidize in dry air at room temperature but is quickly oxidized in moist air or in dry oxygen at about 300°C. Calcium reacts with fluorine at room temperature and with the other halogens at 400°C. Calcium is an excellent reducing agent and is widely used for this purpose. Although in Western countries the aluminothermic process has completely replaced the electrolytic method, electrolysis is believed to be the method used for calcium production in the People's Republic of China and the Commonwealth of Independent States (CIS). Because of its extreme chemical reactivity, calcium metal must be carefully packaged for shipment and storage. The metal is packaged in sealed argon‐filled containers. Calcium is classed as a flammable solid and is nonmailable. Calcium metal and most calcium compounds are nontoxic. Care must be taken, however, to avoid contact with water owing to the exothermic liberation of hydrogen and the resulting explosion hazard. Direct alloying of the pure metals is normally used in the production of 80% calcium–magnesium, 70% magnesium–calcium, and 75% calcium–aluminum alloys.
Aluminum Oxide (Alumina), Calcined, Tabular, and Aluminate Cements
Authors: MacZura George
Published: July 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
‐Al
2
O
3
. 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%

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(44
µ
m) using 85–90% Al
2
O
3
ceramic 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
µ
m. This broad selection enables closer shrinkage control of high tech ceramic parts. Tabular alumina is a high density, high strength form of
α
‐Al
2
O
3
made 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 Chloride
Authors: Vrana Lisa M.
Published: July 2004

Calcium chloride, CaCl
2
, is a white, crystalline salt that is very soluble in water. Solutions containing 30–45 wt % CaCl
2
are used commercially. Of the alkaline‐earth chlorides it is the most soluble in water. It is extremely hygroscopic and liberates large amounts of heat during water absorption and on dissolution. It forms a series of hydrates containing one, two, four, and six moles of water per mole of calcium chloride. Commercial applications of calcium chloride and its hydrates exploit one or more of its properties with regard to aqueous solubility, hygroscopic nature, and the heat gained or lost when one hydrated phase changes to another. Because of its high solubility in water, calcium chloride is used to obtain solutions having relatively high densities. Viscosity is an important property of calcium chloride solutions in terms of engineering design and in application of such solutions to flow‐through porous media. In the United States the principal route for making calcium chloride is by the evaporation of underground brines. Significant markets in the United States are for deicing during the winter, and roadbed stabilization, and as a dust palliative during the summer. Use as an accelerator in the ready‐mix concrete industry is sizable, but there is concern about the possible corrosion of steel in, highways and buildings. Calcium chloride is also used in oil and gas well drilling. Food‐grade calcium chloride is used in cheese making to aid in rennet coagulation and to replace calcium lost in pasteurization. In the canning industry it is used to firm the skin of fruit such as tomatoes, cucumbers, and jalapenos. Food‐grade calcium chloride is used in the brewing industry as a basic component of certain beers. Calcium Chloride is not considered to be harmful to the environment. Above certain levels chloride is toxic to plants and animals.
Caprolactam
Authors: L. Crescentini William B. Fisher
Published: July 2004

Caprolactam (2‐oxohexamethylenimine, hexahydro‐2
H
‐azepin‐2‐one) is one of the most widely used chemical intermediates. However, almost all of the annual production of

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is consumed as the monomer for nylon‐6 fibers and plastics. Cyclohexanone, which is the most common organic precursor of caprolactam, is made from benzene by either phenol hydrogenation or cyclohexane oxidation. Caprolactam is a white, hygroscopic, crystalline solid at ambient temperature, with a characteristic odor. It is very soluble in water and in most common organic solvents and is sparingly soluble in high molecular weight aliphatic hydrocarbons. Molten caprolactam is a powerful solvent for polar and nonpolar organic chemicals. The low melting point of caprolactam and its stability and low viscosity form the basis for commercial transportation as a liquid in insulated tank cars or trucks. Caprolactam is an amide and therefore undergoes the reactions of this class of compounds. It can be hydrolyzed,
N
‐alkylated,
O
‐alkylated, nitrosated, halogenated, and subjected to many other reactions. All commercial processes for the manufacture of caprolactam are based on either toluene or benzene, each of which occurs in refinery BTX‐extract streams. Alkylation of benzene with propylene yields cumene, a source of phenol; ca 10% of U.S. phenol is converted to caprolactam. Worldwide caprolactam demand increased by about 2% per year during the 1980s, and similar growth is expected into the 1990s. DSM America produces caprolactam only for merchant sales, both domestic and foreign. BASF is a customer, following acquisition of Enka's U.S. fiber and plastics plants, and also a captive producer of caprolactam. Allied‐Signal's production is primarily captive for nylon‐6 fibers and plastics, but substantial amounts are supplied to the export market. Caprolactam has a low order of toxicity. It presents no appreciable health hazard if it is handled properly. Prolonged exposure to dust or vapors causes irritation of eyes, mucous membranes, and skin; inhalation may cause irritation of the respiratory tissues. Skin contact, if prolonged, can lead to dermatosis. A thorough wash with water, in which caprolactam is very soluble, or with soap and water, normally is sufficient to remove caprolactam from contaminated parts of the body. Caprolactam has been extensively tested for its mutagenic potential. Based on the overall weight of evidence, caprolactam would be considered nonmutagenic.
Chloroformates and Carbonates
Authors: Kreutzberger Charles B.
Published: July 2004

The chemistry of carbonic and carbonochloridic esters, commonly referred to as chloroformates and carbonates, is reviewed. These materials are highly reactive with a variety of functional groups and lead to synthetic intermediates for use in pesticides, perfumes, drugs, polymers, dyes, and fuel additives. This article emphasizes the commercial aspects of the carbonate and chloroformate chemistry, including physical and chemical properties, manufacturing processes, analytical test methods, health and effects, environmental aspects, storage, transportation, and uses.
Carbon Tetrachloride
Authors: Holbrook Michael T.
Published: July 2004

Carbon tetrachloride at ordinary temperature and pressure is a heavy, colorless liquid with a characteristic nonirritant odor. It was one of the first organic chemicals produced on a large scale. It is produced in the United States by either the total chlorination of various hydrocarbons or chlorinated hydrocarbons, or by the chlorination of carbon disulfide. U.S. capacity has been estimated at about 273,000 t/yr. Production can be varied in favor of more coproduct perchloroethylene. Projected growth rates of

, per year are probably overstated and actual production will probably fall even faster. The primary use of carbon tetrachloride, CFC‐11 and CFC‐12, will be banned by the Montreal Protocol by the year 2000. Carbon tetrachloride is regulated under a number o ederal and state laws.
Coal Conversion Processes, Carbonization
Authors: Kaegi Dennis , Addes Valery , Valia Hardarshan , Grant Michael
Published: July 2004

Carbonization of coal entails heating coal to high temperatures in the absence of oxygen to distill out tars and light oils. This process is used to produce metallurgical coke for use in iron making blast furnaces and other smelting processes. A gaseous by‐product referred to as coke oven gas or coal gas is also formed along with ammonia, water, and sulfur compounds. Coke over gas is a valuable heating fuel. Other carbonization by‐products are usually refined within the coke plant to produce commodity chemicals.

Coking coals and the various coal constituents that lead to the production of high quality cokes are described. The carbonization process, including the coking mechanism and design of coke ovens, is discussed as are coke properties and coke uses.
Carbon Dioxide
Authors: Pierantozzi Ronald
Published: July 2004

Carbon dioxide is valuable as a chemical intermediate, a liquid refrigerant, and a source of inert gas. It is produced from natural gas wells, lime‐kiln operations, and several other important processes. Most of the significant industrial processes for the production of CO2are reviewed in this article. Methods of purification include reaction and potassium permanganate, reaction with potassium dichromate, adsorption using activated carbon, liquefaction, and solidification. Numerous uses including food freezing, enhanced oil recovery, chemical manufacturing, refrigeration, and carbonation are reviewed.
Carbon Monoxide
Authors: George Christine
Published: July 2004

Carbon monoxide, gaseous in normal atmospheric conditions, is colorless, odorless, and highly toxic. Carbon monoxide is a co‐product, along with hydrogen, in synthetic gas (syngas) production. Several technologies are used to produce syngas and these are discussed. Gas pipeline is a cost‐effective way to manufacture and deliver carbon monoxide to the user. Industrially produced carbon monoxide is used in the chemical industry for the synthesis of several compounds, such as acetic acid, polycarbonates, acetic anhydride, polyketones, etc. The demand for carbon monoxide as a raw material for chemical synthesis is expected to continue. Carbon monoxide is also a by‐product of highway vehicle exhaust. Other sources are from industrial emissions and fuel combustion. Hazards associated with carbon monoxide use derive from its toxicity and flammability.
Carbon Disulfide
Authors: Smith David E. , Timmerman Robert W.
Published: July 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. Most of carbon disulfide produced worldwide goes 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.
Carbapenems and Penems
Authors: Southgate Robert , Osborne Neal F.
Published: July 2004

In the period up to 1970 most β‐lactam research was concerned with the penicillin and cephalosporin group of antibiotics. Since that time, however, a wide variety of new mono‐ and bicyclic β‐lactam structures have been described. The carbapenems originated from natural sources; the penem ring and its derivatives are the products of the chemical synthetic approach to new antibiotics. The chemical names are: 7‐oxo‐(R)‐1‐azabicyclo[3.2.0]hept‐2‐ene‐2‐carboxylic acid, C7H7NO3, and 7‐oxo‐(R)‐4‐thia‐1‐azabicyclo[3.2.0]hept‐2‐ene‐2‐carboxylic acid, C6H5NO3S, respectively. Carbapenems include thienamycin (C11H16N2O4S), MM 4550 (C13H16N2O9S2), MM 13902 (C13H16N2O8S2), MM 17880 (C13H18N2O2S2), PS‐5 (C13H18N2O4S), carpetimycin A (C14H18N2O6S), asparenomycin A (C14H16N2O6S), and pluracidomycin A (C9H11NO10S2). OnlyS. cattleyaandS. penemfacienshave been reported to give thienamycin. Thienamycin is isolated as a colorless, hygroscopic, zwitterionic solid. Carbapenems are extremely sensitive to many reaction conditions. Many derivatives of the amino, hydroxy, and carboxy group of thienamycin have been prepared primarily to study structure–activity relationships. One consequence of the discovery of the carbapenem natural products has been the development of new synthetic methods. Only chemical synthesis could provide the quantities ofN‐formimidoyl thienamycin (MK 0787) necessary for clinical trials and commercial production. A synthetic approach that involves the [3,4] bond formation using a carbene insertion reaction has been highly successful. A second method makes use of the lactone from acetone dicarboxylate. Thienamycin, the olivanic acids, and the majority of carbapenems are highly active broad‐spectrum antibiotics. Of the natural products, thienamycin is the most potent. Unlike carbapenems, no penems have been found in nature. The penem acid was shown to possess antibacterial activity in spite of its rather limited stability. Penems include SCH 29482 (C10H13NO4S2), SCH 34343 (C11H14N2O6S2), FCE 221201 (C10H12N2O6S), and others. 6‐Unsubstituted penems exhibit good activity against both gram‐positive and gram‐negative bacteria. Extensive carbapenem and penem antibiotic research has been ongoing since thienamycin was discovered in 1978. However, only the imipenem–cilastatin combination has become a commercial product. Meropenem was expected to be the second carbapenem on the market.
Metal Surface Treatments, Case Hardening
Authors: Brooks Charlie R.
Published: July 2004

The performance of many metallic components can be markedly improved by developing a surface region, the case, which is harder than that of the underlying region, the core. Case hardening processes, in which the original surface is an integral part of the case, may involve a physical or a chemical change at the surface. Processing may be accomplished through the use of heat or other methods such as plastic deformation or ion implantation. Small atoms, ie, first row elements, deposited in interstitial positions harden metallic components.

The various case hardening processes used for steels are discussed. Carburizing and nitriding, the most common methods employed, and the resultant case‐hardened steels are compared.
Castor Oil
Authors: Naughton Frank C.
Published: July 2004

Castor oil, a renewable vegetable oil resource derived from the seed ofRicinus communis, is a versatile material that finds use as an industrial article of commerce. Castor oil is the only principal industrial oil that consists of 90% of the glyceride of a hydroxy acid, ricinoleic acid. The presence of the hydroxyl group in addition to the olefinic linkage, accounts for a unique combination of physical and chemical properties.

World production, processing, and utilization of the oil to produce a variety of oleochemcals, are described as are the properties and chemical modifications of castor oil and its derivatives. Processes for recovery of the oil and meal, dehydration, polyamide polymer formation, sulfonation, alkali fusion, pyrolysis, hydrogenation, alkoxylation, and urethane reactions are discussed, and applications for the various materials are presented.
Catalysis, Phase‐Transfer
Authors: Dehmlow Eckehard Volker
Published: July 2004

Phase‐transfer catalysis (PTC) is a method that allows reactions to occur in two‐phase systems in an easy and efficient way. Typically salts, dissolved in water or as solids, react with organic substances in organic nonpolar solvents. Catalysts are mostly quaternary ammonium or phosphonium salts, or polyethylene glycols. Alternatively, much more expensive crown ethers or cryptands are applied, predominantly for laboratory purposes. Mechanistically, most of the common PTC applications involve the extraction of anions into nonpolar organic media wherein they have much higher reactivities than under normal conditions as a result of lesser solvent interactions.

Scope, mechanism, and examples of PTC are discussed, and the potential industrial importance of the method is stressed. Reactions that are mentioned in some detail include displacements, ester formation, ether formation, alkylation of carbanions, nucleophilic aromatic substitution, alkylation ofN‐heterocycles, polymerization of acrylates, oxidations, and carbene generation.
Catalysis
Authors: Gates Bruce C.
Published: July 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.
Hydrocarbons, C
1
–C
6
Authors: Eastman Alan D. , Mears David
Published: July 2004

Eastman, Alan D. (Phillips Petroleum), and Mears, David E. (Unocal Corp.). This article covers the first three members of the alkane family, methane, ethane, and propane; the two isomeric butanes; the three isomeric pentanes; hexanes; and cyclohexane. Their properties, manufacture, and uses are described.Natural gas is the principal source of methanes, ethanes, and propane. Butanes are recovered from natural gas and petroleum refining streams. Pentanes occur in straight‐run gasoline and certain refining streams. Hexane and cyclohexane can be obtained from crude oil. High purity cyclohexane is made by hydrogenation of benzene.Principal uses of the alkanes are as fuels and as raw materials for essential chemical intermediates, notably ethylene from ethane and propane and nylon precursors from cyclohexane.
Cellulose
Authors: French Alfred D. , Bertoniere Noelie R. , Brown R. Malcolm , Chanzy Henri , Gray Derek , Hattori Kazuyuki , Glasser Wolfgang
Published: July 2004

This article covers nomenclature, sources, preparation, uses, microcrystalline cellulose, structural chemistry, reactions, solvents, and liquid crystals. Cellulose for commercial purposes comes mostly from wood and cotton, whereas cellulose for research comes from bacteria, algae, and ramie (also a textile fiber). Preparation includes pulping and purification, with an alternative method of steam explosion. The pore structure of cellulose is mentioned, along with the buildup of cellulose molecules into entire fibers. Emphasis is given to cellulose crystal structure. Recent research has provided structures with much better resolution for two crystal forms. Most native cellulose is a mixture of two crystalline phases. Cellulose solutions are important to the rayon and cellophane industries, and new solvents are of interest because they may lessen pollution and might permit commercial production of stronger cellulosic materials through the formation of liquid crystals. Figures include the chemical and physical structures of the molecule, including in solution, X‐ray diffraction patterns, the structure of a microfibril, and the unit cell structures of cellulose I–IV.
Cellulose Ethers
Authors: Majewicz Thomas G. , Podlas Thomas J.
Published: July 2004

Cellulose ethers is the common terminology for a group of cellulose derivatives that are soluble in aqueous or organic media. They are additives in many formulations and function primarily to control solution rheology. This article surveys the chemistry, properties, and characterization methods common to cellulose ethers and their manufacture and provides general health and safety factors. In the discussion of commercial cellulose ethers, greater detail for individual cellulose ether compositions, including carboxymethylcellulose, hydroxyethylcellulose and its mixed ethers, methylcellulose and its mixed ethers, ethylcellulose, hydroxyethylethylcellulose, and hydroxypropylcellulose is offered.
Fractionation, Blood, Cell Separation
Authors: Sibinga Theodore Hein Smit
Published: July 2004

With the advance of medical sciences, blood transfusion has transformed into blood component therapy. Human blood can be separated into its components, ie, red cells, white cells, platelets, and plasma; each serves its own function in the body. Minimizing risk of transmitting blood‐borne disease has driven blood transfusion toward maximizing the yield of a specific blood component from a specific blood donor. The blood component collected depends on need. Plasma is collected primarily for the procurement of coagulation factors, red cells are transfused in order to increase the oxygen carrying capacity of a patient, and platelets are applied to secure coagulation of the blood.

Based on biological and physical differences between the blood components, technologies have been developed to separate blood from a blood donor or patient, collect those components needed for transfusion, and return the other components to the donor.

Many cell separation methods are based on the formation of layers by mass density gradient using centrifugal separation chambers, eg, countercurrent separation and elutriation. The Beckman elutriation chamber and Haemonetics bowl technology are two such methods. Filtration technologies using advanced biomaterials are applied in the removal of leukocytes from red blood cell and platelet concentrates.
Centrifugal Separation
Authors: Letki Alan , Corner‐Walker Nick
Published: July 2004

Separation by density difference, compaction, 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 process materials; 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; decanter; preparation; zonal; tubular; perforate basket; inverting filter; conical; and continuous single‐ and multiple‐stage pusher centrifuges are reviewed. For a brief discussion of gas centrifuges and their use in uranium enrichment, please see the previous editions.
Ceramics, Ceramic Processing
Authors: Ewsuk Kevin G.
Published: July 2004

In the manufacture of ceramic components, chemical composition and microstructure are specified to optimize the properties (eg, mechanical, electrical, and magnetic) of the finished product for a given application. Optimum properties are achieved by developing and refining processes to produce a target microstructure, and by controlling processes to minimize the concentration and scale of the defects in the finished part. The tolerance of the finished ceramic to defects determines the degree of control that must be exercised during processing.

Ceramic component fabrication involves simultaneously optimizing multiple processes ranging from raw materials beneficiation to post‐sinter machining. To manufacture reliable ceramic components with reproducible properties, process–microstructure–property relationships must be understood and controlled during processing. These relationships can be determined by characterizing the ceramic raw materials, mixes, and the formed ceramic body intermittently during the various stages of processing and after final thermal consolidation. Established relationships between processing, microstructure, and properties can be applied to control manufacturing processes and optimize properties, and to identify and correct process deficiencies when less than optimal properties are obtained.
Cerium and Cerium Compounds
Authors: Kilbourn Barry T.
Published: July 2004

Cerium is the most abundant member of the lanthanide series, those elements having 4felectrons. It is found in nature in the presence of other lanthanides and this mix is often used commercially as a cerium source without separation. Mischmetal, a metallic mix of cerium and other of the lighter lanthanides, is used in the steel industry, in lighter flints, and as getters. Lanthanide concentrate, an oxide mix that includes cerium oxide, is used in some fluid cracking catalysts.

Cerium is unique within the lanthanide series because it has two stable oxidation states. Many of the uses of cerium and cerium compounds center around the redox chemistry of the Ce(IV)/Ce(III) couple. Cerium oxide acts as a stabilizer improving oxidation resistance for alloy systems, polymers, and automotive catalytic converter catalysts. Cerium compounds are present in optical coatings, in phosphors for cathode ray tubes, and in paints.
Cesium and Cesium Compounds
Authors: Ferguson William , Gorrie Dena
Published: July 2004

Cesium is the most chemically active and rare of the naturally occurring Group 1 (IA) alkali metals. It is generally produced from pollucite by acid digestion to an intermediate cesium compound followed by thermochemical or electrolytic reduction. Production routes and properties of cesium and cesium compounds are described. Uses of cesium and cesium compounds continue to grow in electronics, in catalysts and organic synthesis, in analytical instrumentation, in biotechnology, and in medical applications. Cesium usage has also shown potential in such areas as magnetohydrodynamic power generation.
Chelating Agents
Authors: Howard William L. , Wilson David
Published: July 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 that 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.
Chemiluminescence, Analytical Applications
Authors: Nakashima Kenichiro
Published: July 2004

Chemiluminescence (CL) has many advantageous features as a tool of detection in instrumental analysis, including sensitivity, selectivity and simplicity. A CL reaction needs no excitation light source, thus, it is not accompanied with any scattering light. This results in a large signal‐to‐noise (S/N) ratio and consequently, a substantial increase in detector's sensitivity. To date, several kinds of CL reactions have been clarified on their reaction mechanisms. Generally, concentrations of the substrates or catalysts in each CL reaction can be determined by measuring the CL generated. Among the CL reactions, luminol (5‐amino‐2,3‐dihydro‐1,4‐phthalazinedione) derivatives, acridine derivatives, aryloxalate derivatives, and ruthenium derivatives have frequently been utilized in analytical applications. In this article, representative analytical applications of CL in liquid phase for the determination of a variety of compounds are described.
Chemicals from Brine
Authors: Butts David
Published: July 2004

Over a billion tons of brine are handled yearly by industries to produce minerals and chemicals. This makes it one of the largest processed ores in the world. These minerals and chemicals are used in the processing of fertilizers, detergents, paper, plastics, preservatives, foodstuffs, pharmaceuticals, metals, and glass. Sodium chloride alone is used in 14,000 different products.

Compounds of boron, bromine, calcium, iodine, lithium, magnesium, potassium, and sodium are all produced from brine. There is an endless supply of some of these chemicals in the oceans. Most of the brine is concentrated by solar evaporation in shallow ponds that saves energy and eliminates pollution by not burning fossil fuel.
Metal Surface Conversion Treatments
Authors: Petschel Michael , Hart Robert
Published: July 2004

Metals, important materials for construction and manufacture, corrode in certain environments limiting the lifetime of manufactured metal goods. To protect from corrosion and to confer paint adhesive properties to metal surfaces, chemical pretreatment conversion coatings are widely used.

The most common metal surface treatments are iron, zinc, or chromium phosphating, chromating, and anodizing. An overview of the mechanism of coating formation, process operation and control considerations, coating characteristics, coloring procedures, and important applications for various coatings is given. Environmental considerations for chemical conversion coatings and by‐products of conversion coating operations are also discussed.
Chlorosulfonated Polyethylene
Authors: Ennis Royce
Published: July 2004

Chlorosulfonated polyethylene represents a group of chemically modified polyolefins containing pendent chlorine and sulfonyl chloride groups and having useful synthetic elastomer properties. They are derived from the action of a mixture of chlorine and sulfur dioxide, sulfuryl chloride and a weak base, or sulfuryl chloride and chlorine on preformed polyolefin polymers in the presence of an initiator. Although the reaction is normally carried out batchwise in a carbon tetrachloride solution, other solvents and process schemes have been successfully used. The resulting polymer may contain 20–60% chlorine and 1–5% sulfur as sulfonyl chloride groups. The pendent chlorine atoms serve to destroy the parent polymer crystallinity and impart useful chemical properties such as resistance to oil, oxidizing chemicals, ozone, and heat. The sulfonyl chloride groups react with divalent metal oxides, sulfides, or radical traps to form stable cross‐links. The raw polymer and vulcanizate mechanical properties are controlled by the molecular weight, molecular‐weight distribution, and chain branching of the parent polyolefin.

The technology has been extended to include copolymers and functionally grafted homopolymers as base resins. These new types, along with extensive studies combining the flexibility of the sulfonyl chloride cure site with specific cross‐linking agents, stabilizers, and reinforcing agents, have produced a broad array of useful products, ie, coatings, adhesives, hose, tubing, automotive belts, etc.
Chlorosulfuric Acid
Authors: McDonald C. E.
Published: July 2004

Chlorosulfuric acid, more widely known as chlorosulfonic acid, is a strong mineral acid made by reacting equimolar quantities of hydrogen chloride and sulfur trioxide. Its structure is analogous to sulfuric acid: the chloride replaces a hydroxyl group. Chlorosulfuric acid is a highly reactive chemical used principally in organic synthesis as a sulfating, sulfonating, or chlorosulfonating agent. Its main applications are an intermediate in the production of synthetic detergents, surfactants, and pharmaceuticals. It is also used in the production of dyes and pigments, ion‐exchange resins, pesticides, and plasticizers.

Commercial‐grade chlorosulfuric acid has a purity of 99+%. When exposed to the atmosphere, it reacts with the moisture present to form dense white clouds of sulfuric acid and hydrochloric acid mists. It has been used as a smoke screen in wartime.
Chloric Acid and Chlorates
Authors: Mendiratta Sudhir K. , Duncan Budd L.
Published: July 2004

Sodium chlorate is the primary raw material for the manufacture of chlorine dioxide, a bleaching agent in the pulp and paper industry. Chlorine dioxide substitutes for chlorine in pulp bleaching, most ore of the sodium chlorate produced is used in the bleaching process. 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. They are strong irritants.

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.