bluuebunny/crossref_metadata_2025 huggingface dataset:
Industrial Antimicrobial Agents
Authors: McEntee Thomas
Published: July 2004

Industrial antimicrobial agents are chemicals used to prevent the adverse consequences of microbiological activity in processes and products. They are targeted against bacteria, mold, and fungi. Applications of industrial antimicrobial agents fall into two categories: process uses and preservation uses. They are found in swimming pool sanitizers, cooling water treatments, metalworking, petroleum recovery, pulp and paper processing, paint, caulks and adhesives, laundry sanitizers, textiles, plastics, and cosmetics. The key trend affecting this industry is the regulation of products and their uses by the U.S. Environmental Protection Agency. These regulations have curtailed the introduction of new ingredients, selectively limited the markets for a number of products, and eliminated products by suspension or cancellation. This article lists and discusses materials used and their statuses, as well as formerly used agents and biocides under development.
Enzyme Applications, Industrial
Authors: Nielsen Peder Holk , Malmos Henrik , Damhus Ture , Diderichsen Boerge , Nielsen Henrik Kim , Simonsen Merete , Schiff Hans Erik , Oestergaard Anders , Olsen Hans Sejr , Eigtved Peter , Nielsen Tage Kjaer
Published: July 2004

Enzyme technology has been used in industrial applications since ancient Greece. The era of modern industrial enzyme technology began in 1874 with the extraction of chymosin from dried calves' stomachs. The detergent industry is the largest user of industrial enzymes, utilizing proteases, amylases, lipases, and cellulases to remove soilings, increase softness, and protect fabric. The starch industry, which was the first significant user of enzymes, uses pullanases and a variety of amylases for the liquefication, saccharification, and isomerization of starches. Enzymes also find use in the textile, tannery, pulp and paper production, and animal feed industries. Another important industrial application of enzymes is in the food industry, ie, dairy, bakery, brewing, and protein modification industries. Industrial applications of enzymes are regulated.

Production of industrial enzymes involves fermentation, recovery, and purification. A variety of host microorganisms are used to optimize fermentation techniques. Catalytic activity, kinetics, and response to temperature and pH affect the use of enzymes in industrial applications. Genetic engineering of enzymes is used to modify and improve natural enzymes, including increased protein production and increased genetic and product stability.
Furnaces, Electric, Induction Furnaces
Authors: Sommer Richard A.
Published: July 2004

Induction furnaces utilize the phenomena of electromagnetic induction to produce an electric current in the load or workpiece. This current is a result of a varying magnetic field created by an alternating current in a coil that typically surrounds the workpiece. Power to heat the load results from the passage of the electric current through the resistance of the load. Physical contact between the electric system and the material to be heated is not essential and is usually avoided. Nonconducting materials cannot be heated directly by induction fields.

The efficiency of an induction furnace installation is determined by the ratio of the load useful power to the input power drawn from the utility. Losses that must be considered include those in the power converter transmission lines, coil electrical losses, and thermal loss from the furnace. A unique capability of induction heating is apparent in its ability to heat the surface of a part to a high temperature while the interior remains at room temperature. Induction heating is used to heat steel reactor vessels in the chemical process industry. Induction melting applications almost always contain the liquid metal charge within a hearth formed by a suitable refractory material. Coreless furnaces derive their name from the fact that the coil encircles the metal charge but the coil does not encircle a magnetic core. Channel induction furnace is one in which the energy for the process is produced in a channel of molten metal that forms the secondary circuit of an iron core transformer. The primary circuit consists of a copper coil which also encircles the core.
Carbides, Industrial Hard
Authors: Stoll W. M.
Published: July 2004

The four most important hard carbides for the production of cobalt‐cemented (hard metal) carbide compositions are tungsten carbide (WC), and the cubic carbides titanium carbide (TiC), tantalum carbide (TaC), and niobium carbide (NbC). Of these, tungsten carbide is of paramount importance, in most cases forming a foundation‐alloy to which smaller quantities of the cubic carbides are added to affect changes in metalcutting insert and other tool properties. In cemented carbide compositions for machining applications, preformed binary and ternary solid solutions (mixed crystals), made up of the primary carbides and based on the solven powers of the cubic carbides for WC, comprise important portions of the hard phases in cutting‐insert microstructures. WC–TiC and WC–TiC–TaC(NbC) are of great importance among carbide solid solutions. WC, essentially unalloyed, is the paramount hard phase in metal‐cutting tools for short‐chipping materials, forming tools, and in tools used by the mineral, transportation, and construction industries. Auxiliary hard carbides of chromium, molybdenum, vanadium, hafnium, and zirconium are used to achieve secondary property enhancement. In general, the hard carbides are produced by reaction of elementary carbon or hydrocarbons and metals and metal compounds at high temperatures. Methods include carburization by thermal diffusion, by menstruum process, by thermochemical reaction, by reduction of metal halides and, to a minor extent, by fusion. Several categories of refining services support manufacturers of cemented carbides: extraction of tungsten as tungstic acid, WO3, or ammonium paratungstate from tungsten‐mineral concentrates, and extraction of oxides of titanium, tantalum, and niobium from mineral concentrates of those metals. Integrated carbide manufacturers carry out reduction of the metal oxide to metal powder, preparatory to carburization. Equipment and process departures to produce submicron and ultrafine tungsten carbide powders include carburization by gaseous fluid‐bed processes and chemical vapor reaction.
Peroxides and Peroxide Compounds, Inorganic Peroxides
Authors: Steiner Norbert , Eul Wilfried
Published: July 2004

Inorganic peroxides and peroxo compounds, with the exception of hydrogen peroxide, are described. Ozonides and superoxides are also included. Emphasis is placed on the commercially important main group species such as the sodium peroxoborates, sodium carbonate peroxohydrate, peroxodisulfate salts, calcium peroxide, sodium peroxide, and potassium superoxide. Most of these compounds are made from hydrogen peroxide; some, such as the peroxodisulfates, are made electrochemically. Applications of inorganic peroxides and peroxo compounds include household detergents, polymerization catalysts, effluent treatment, organic synthesis as well as uses in pyrotechnics, dough conditioning, hydrometallurgy and medicine.
Titanium Compounds, Inorganic
Authors: Fisher James , Egerton Terry A.
Published: July 2004

Properties and applications of technologically important inorganic compounds of titanium are surveyed. The most important compound is titanium dioxide which, because of its high refractive index, is manufactured as a white pigment at a scale of ca\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${4\times 10^{6}{\hskip0.167em}{\hskip0.167em}{\rm{t}}/{\rm{yr}}}$\end{document}. Raw materials and pigment production processes are reviewed. Mixed oxides, eg, barium titanate, are important raw materials for electroceramics.

Titanium hydrides provide a convenient method of hydrogen storage. Titanium boride, titanium carbide, and titanium nitride are used as components of hard materials, eg, for cutting tools. They are electrically conducting.

The chlorides are the most important halides. Titanium trichloride is the basis of widely used polymerization catalysts. Titanium tetrachloride is an intermediate in the production of both titanium metal and (via the chloride process) titanium dioxide pigment. Titanium dioxide pigment is also made (in the sulfate process) by precipitation from solutions of titanium in sulfuric acid. Titanium sulfides may be used as cathodes in high efficiency batteries. The properties of some titanium compounds with silicon and phosphorus are reviewed. Analytical methods and health and safety aspects are summarized.
Cellulose Esters, Inorganic Esters
Authors: Shelton Michael C.
Published: July 2004

Inorganic esters of cellulose have a valuable place in history, from the birth of the plastics industry to elucidation of the genetic code. It is important not to forget the large number of applications in which these materials have played a role: coatings, explosives, pharmaceuticals, membranes, and synthetic intermediates. Though inorganic esters of cellulose have been around for >100 years, these materials remain important tools for coatings scientists, explosives experts, and biochemists. This report provides a summary of work on inorganic esters of cellulose, including cellulose nitrate, cellulose phosphate, cellulose sulfate and cellulose sulfonates.
Electrochemical Processing, Inorganic
Authors: Grotheer Morris P.
Published: July 2004

Electrochemical processes are used to produce an array of reactive inorganic chemicals and metals. The most reactive materials, strongest oxidants, and strongest reductants are produced electrochemically at anodes and cathodes, respectively. Process technology for the production of each electrochemical is unique. Power supplies and electrolytic cells are the distinguishing features of electrochemical processes. Electrolytic cells use direct current and are designed to be process specific. Every cell consists of an anode, a cathode, and container. Cells may be monopolar or bipolar, with or without separators, and equipped to handle aqueous solutions or fused salt electrolytes. Industrial processes described include electrolysis of chloride solutions and production of manganese dioxide, fluorine, permanganate, and hydrogen peroxide. The electrolysis of water and production of heavy water are also described. Processes for electrowinning of metals from aqueous solutions and from fused salts are discussed as are electrochemical processes for hazardous waste treatment systems.
Pigments, Inorganic
Authors: Novotny Mirek , Solc Z. , Trojan M.
Published: July 2004

Inorganic pigments, black, white, or colored, are an integral part of many decorative and protective coatings. These materials are produced and marketed as fine powders which are then dispersed in the desired media. Inorganic pigments are used for the mass coloration of plastics, fibers, paper, rubber, glass, cement, glazes, and porcelain enamels, as well as for colorants in printing inks, cosmetics, and markers such as crayons. Pigment properties including particle size, tinting power, and hiding strength are discussed.

Inorganic pigments of largest commercial interest are the white titanium dioxide; the colorful natural and synthetic iron oxides; various zinc compounds; and carbon black. Many transition‐metal and some rare‐earth compounds are used as chromophores in host oxides such as spinel to produce stable and affordable pigments. Environmentally benign, colorfast replacements are being sought for the historically popular, highly colored lead and cadmium compounds which have proven toxic.
Inorganic High Polymers
Authors: Roy Aroop K.
Published: July 2004

Since the development and commercialization of the polysiloxanes, a number of linear, inorganic‐backbone polymers have been reported. Most prominent among these are the polyphosphazenes and the polysilanes. Some, like poly(sulfur nitride) and the polycarborane–siloxanes, have manufacturing or stability problems. The heterophosphazenes, the alkyl/arylphosphazenes, and the polyoxothiazenes are relatively new and awaiting development and breakthrough in manufacturing technology for a number of potential applications. The polyphosphazenes with PO and PN‐bonded substituents (synthesized by a ring‐opening polymerization–substitution route) are the most mature and have seen limited manufacturing and commercialization in the area of specialized rubber markets. These polymers are extremely versatile in terms of potential applications in the areas of biomedical technology, elastomers, solid‐state batteries (via ionic conduction), catalysis, etc. The poly(alkyl/arylphosphazenes), synthesized by a polycondensation route, possess many of the properties of the PO‐ and PN‐substituted polymers and appear to be suitable for application as wide temperature‐range elastomers, thermoplastic polymers, and biomaterials. The polysilanes, which can be prepared by a number of methods are a unique class of polymers in exhibiting σ‐conjugation along the backbone. The majority of the developing applications for these polymers are based on this phenomenon, which leads to near‐uv photoabsorption, thermo‐ and piezochromism, and photodegradation. For many of the existing and developing inorganic‐backbone polymers with potential for commercial applications, a pivotal aspect for manufacture is relative ease of industrial scale‐up. This translates into readily accessible and relatively inexpensive starting materials, in addition to a process that allows flexibility with equipment and is environmentally friendly.
Insulation, Electric
Authors: Moscovici Armand
Published: July 2004

Moscovici, Armand (The Kerite Co.). Insulated wire and cables represent a significant industry of more than $10 billion in 1990. The largest segments of various types and designs are building wires, electronic and data communication wires, power cables, fiber optics, automotive wires, magnet and transformer wires, and specialty wires. Power cables have the most complicated designs. Depending on the voltages used, power cables can contain many layers, each one made of specially developed materials with very specific characteristics and functions.

The electrical properties of most concern to insulation are dielectric strength, electrical resistance, dielectric constant, power factor, and corona resistance. In power cables electrical and water treeing characteristics influence lifetimes, especially when the service is under high voltages and wet conditions. In coaxial data communication wires, the electric properties related to the dielectric constant determine the quality of the signal: impedance, capacitance, attenuation, crosstalk, and time delay, and velocity of propagation. Typical materials used in various insulated wires and cables are polyethylene, polypropylene, silicone rubber, ethylene–propylene rubber, fluoroplastics, poly(vinyl chloride), and other plastics to lesser extents. Vol. 14, pp. 627–647, 28 refs. to January 1994.
Insulin and Other Antidiabetic Agents
Authors: Shoelson Steven E.
Published: July 2004

Diabetes mellitus, a metabolic disturbance of carbohydrate, fat, and protein metabolism, results from too little insulin production or a failure of insulin to exert its effects. Insulin‐dependent diabetes is always treated with insulin, whereas noninsulin‐dependent diabetes can be treated by diet or with insulin or additional oral hypoglycemic agents. Therapeutic insulins can be prepared either from animal sources or biosynthetically. In addition, insulin can be mixed with other agents to provide therapeutic formulations having altered rates of absorption. Oral antidiabetic agents include sulfonylurea compounds, biguanides, and inhibitors of α‐glycosidase. Various aspects of the pathophysiology and treatment of diabetes, and detailed discussion of the agents used to treat diabetes, are included herein.
Integrated Circuits
Authors: Sawchyn Irene
Published: July 2004

Integrated circuits consist of many devices or components each of which has a specific combination of conducting, semiconducting, and nonconducting layers that performs a single electrical function. Many of these devices are connected (integrated) into a complete integrated circuit or chip, and thousands of chips are formed simultaneously on a wafer. Increased miniaturization of device features, together with an increase in chip size and a concomitant increase in the number of chips per wafer, has led to increasingly sophisticated electronic products. Silicon technology predominates in the semiconductor industry. Thus developments in silicon technology, as well as developments in the manufacture of devices on silicon, drive advances in integrated circuitry. The basics of silicon technology including crystal growth and wafer preparation are described. The fabrication processes that deposit layers such as silicon epitaxy and oxidation, dielectric film formation, and metallization are discussed. Those techniques utilized to modify the electrical properties of the layers using dopants, and those employed for patterning and process integration, are presented as are the instrumental techniques that enable the analysis of the resultant circuits.
Olefin Polymers, Introduction
Authors: Kissin Yury V.
Published: July 2004

Polyethylene (PE) resins are a large family of semicrystalline polymers used mostly as commodity plastics. The resins are essentially linear polymers with ethylene molecules as the main building block, although most PE molecules also contain branches in their chains. Industry produces a large variety of PE resins. They may differ in molecular weight; in their origin and type of branch; in the content of the branches; and in the uniformity of the branching distribution between different polymer chains.

Ethylene polymers are manufactured by a number of processes that include polymerization in supercritical ethylene at 150–350°C (with radical initiators, Ziegler catalysts, and metallocene catalysts), as well as catalytic polymerization reactions in solution (at 120–150°C), in a hydrocarbon slurry, or in the gas phase. PE resins are in a large variety of applications, both as commodity resins and, in many cases, as specialty polymers. Their uses include PE film; coatings for paper, 8metal, wire, and glass; household and industrial containers; toys; and different types of pipe and tubing. Because of its versatility, PE has become the largest commercially manufactured polymer product in the world.
Fluorine Compounds, Inorganic, Introduction
Authors: Lindahl Charles B. , Mahmood Tariq
Published: July 2004

Fluorine, the most electronegative element, reacts to form compounds with virtually every other element including xenon, radon, and krypton. Several of its compounds are superacids. The basic fluorine‐containing minerals are fluorite and fluoroapatite, commonly called fluorspar and phosphate rock, respectively. Hydrogen fluoride is the most important industrial fluoride. The principal uses of hydrogen fluoride are to produce aluminum fluoride and synthetic cryolite, fluoropolymers, chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons. Anhydrous or aqueous hydrogen fluoride, the most common reagent for the production of fluorine compounds, can cause painful and severe burns and even death.

A number of elements exhibit their highest oxidation state only as fluorides. Fluorine forms very reactive halogen fluorides. The special properties of fluorides lead to applications such as a flux in steelmaking, as catalysts, and in dentifrice additives and drinking water. In many cases the fluoride is the most volatile compound of an element. Special applications of fluorides arise such as use in uranium isotope enrichment and in applications such as chemical vapor deposition and in ion implantation for semiconductors.
Aluminum Compounds, Introduction
Authors: Sleppy William C.
Published: July 2004

The CAS registry lists 5037 aluminum‐containing compounds exclusive of alloys and intermetallics. The aluminum containing compound having the largest worldwide market is metal‐grade alumina. Second is aluminum hydroxide. Bauxite is the principal ore used for alumina production. Additive applications include those as flame retardants in products such as carpets, and to enhance the properties of paper, plastic, polymer, and rubber products. Significant quantities are also used in pharmaceuticals, cosmetics, adhesives, polishes, dentifrices, and glass. Aluminum sulfate,, also known as alum cake, is industrially produced for major applications as a sizing agent in the paper industry and as a coagulant to clarify municipal and industrial water supplies. In terms of worldwide production, it ranks third behind alumina and aluminum hydroxide. All the halogens form covalent aluminum compounds having the formula AlX3. The most important commercially are the anhydrous chloride and fluoride, and aluminum chloride hexahydrate. The latter is used in pharmaceuticals and cosmetics as a flocculant and for impregnating textiles. The alkyls and aryls, R3Al (in monomer form), are colorless liquids or low melting solids easily oxidized and hydrolyzed when exposed to the atmosphere. Triethylaluminum (TEA), one of the most commercially important members of this family of chemicals, is so reactive it bursts into flame on contact with air, ie, it is pyrophoric, and it reacts violently with water. Special techniques are necessary for the safe handling and use of organoaluminum compounds, which are used commercially in multimillion kg/yr quantities as catalysts or starting materials for the manufacture of organic compounds such as plastics, elastomers biodegradable detergents, and organometallics containing zinc, phosphorus, or tin. Sodium aluminate is used in water purification, in the paper industry, for the after‐treatment of TiO2pigment, and in the manufacture of aluminum‐containing catalysts and zeolite. A large and growing industrial use of aluminum hydroxide and sodium aluminate is the manufacture of synthetic zeolite. Zeolites are aluminosilicates with Si/Al ratios between 1 and infinity. There are 40 natural, and over 100 synthetic, zeolites. Zeolite‐based materials are extremely versatile: uses include detergent manufacture, ion‐exchange resins (ie, water softeners), catalytic applications in the petroleum industry, separation processes, and as an adsorbent for water, carbon dioxide, mercaptans, and hydrogen sulfide.
Iodine and Iodine Compounds
Authors: Lauterbach Armin , Ober Gustavo
Published: July 2004

Iodine is used in a wide variety of fields, among which are included industrial, pharmaceutical, nutritional, agricultural, electrical, and metallurgical. Iodine is produced as a nitrate ore by‐product or from brines or seaweed. As found in nature it has only one stable isotope. Several radioactive isotopes have been prepared and have found use as radiopharmaceuticals or radioactive tracers for medical imaging. Iodine is the only halogen that is solid at ambient temperatures and pressures. Having the highest atomic weight of the common halogens, iodine begins to exhibit metallic properties. Besides exhibiting properties of luster and opacity, it is classed as a semiconductor of electricity. It is an essential human nutrient. Commercially available inorganic and organic compounds are described.
Ionomers
Authors: Rees Richard W.
Published: July 2004

Rees, Richard W. (E. I. du Pont de Nemours & Co., Inc.). Commercial ionomers are copolymers of ethylene with 5–10 wt % methacrylic or acrylic acid, which have been partly neutralized with mono‐ or divalent metal ions, the most important being sodium and zinc. The presence of the ion results in strong ionic forces between the polymer chains. These forces have profound effects on both solid‐state and melt properties, resulting in a spectrum of end uses; this is quite distinct from that of other ethylene‐based resins. The relationships between ionic forces and properties are covered in this article. Information is also presented on manufacture and applications of the products sold as Surlyn, Hi‐Milan, or Iolon resins. Other types of ionomers, such as styrenics, which have been extensively studied but have not become commercial, are also reviewed briefly. Vol. 14, pp. 815–829, 76 refs. to June 1992.
Iron and Steel, Economic Aspects
Authors: Geiger Gordon H.
Published: July 2004

The economics of iron and all of its derivative materials is dominated by the fact that iron is the most widespread and ubiquitous metallic element found in the earth's crust. Iron ore deposits are present and mined on all the inhabited continents. From these ores, iron has been extracted for centuries, through the Iron Age and eventually the Industrial Revolution. The economics of iron production from ore is therefore the starting point, but then the preparation of steel from the base iron incurs further costs. And after centuries of iron products entering the world economies, iron in the metallic form, as iron and steel scrap, is now recycled in significant quantities, having a significant effect on the overall economics of steel. Therefore, in this article, the economics of iron and steel scrap will also be considered.
Iron
Authors: Lepinski J. A. , Myers Jeffrey C.
Published: July 2004

Iron, the fourth most abundant element in the earth's crust, is the world's least expensive, most useful metal. Iron is alloyed with other elements for commercial applications. Iron‐bearing minerals of economic importance are hematite, magnetite, goethite, siderite, ilmenite, and pyrite. These ores can be beneficiated through crushing, grinding, magnetic separation, flotation, electrostatic separation, roasting, sintering, or pelletizing. Iron oxides in the form of pellet, lump, and/or sinter are fed along with coke and limestone into the blast furnace wherein the iron oxide is reduced and melted into hot metal (pig iron); the pig iron is further refined in an oxygen converter to make steel. New technologies are being developed as alternatives to the blast furnace for reducing iron oxide. These include direct reduction and direct smelting processes. In the foundry, ferrous scrap can be melted along with coke in a cupola or induction furnace to make cast iron. Cast iron can be classified into gray, white, malleable, or ductile iron.
Iron by Direct Reduction
Authors: Lepinski J. A.
Published: July 2004

Lepinski, J.A. (Midrex Direct Reduction Corp.). Direct reduction is the process of converting iron ore into metallic iron without melting. Direct reduced iron (DRI) is used as a high quality feed material in electric arc furnace steelmaking, oxygen steelmaking, ladle metallurgy, blast furnace ironmaking, and foundries. Normally 90 to 95% of the iron in DRI is in the metallic form. Carbon is normally present in the DRI to balance any remaining iron oxide, and the level of residual elements is very low. The reduction of iron oxide proceeds from hematite to magnetite to wustite to iron. Some of the iron may combine with carbon to form cementite; DRI having high percentages of cementite is sometimes called iron carbide. The most common reductants are reformed natural gas and coal. The main commercially proven direct reduction processes are discussed. Hot briquetted iron (HBI), a densified form of DRI, is more resistant to reoxidation and corrosion. Vol. 14, pp. 855–872, 7 refs. to April 1994.
Isocyanates, Organic
Authors: Richter Reinhard H. , Priester Ralph D.
Published: July 2004

Isocyanates are highly reactive compounds which have found wide utilities in synthetic transformations and industrial applications. These materials are synthesized by reaction of primary aliphatic or aromatic amines and phosgene (carbonyl dichloride) to form carbamoyl chlorides which are subsequently pyrolyzed to the desired isocyanates. A characteristic reaction of isocyanates and alcohols to form carbamates (urethanes) has been used for the qualitative identification of the latter. Extension of this reaction to difunctional isocyanates and difunctional or polyfunctional alcohols is the basis of the polyurethane industry, with products ranging from flexible and rigid insulating foams to thermoplastic elastomers, coatings, and adhesives, as well as a variety of automotive and recreational products.p‐Toluenesulfonyl isocyanate is used in the synthesis of drugs for diabetics. A unique feature of isocyanates is their tendency to oligomerize or polymerize in presence of catalysts. In addition, isocyanates easily form adducts with carbodiimides, isothiocyanates, ketenes, or with substrates containing activatedorbonds. Low boiling isocyanates are strong lachrymators and irritants. Several isocyanates and their precursors have been identified as mutagens. Guidelines for safe handling of isocyanates are discussed. Vol. 14, pp. 902–934, 100 refs. to January 15, 1993.
Isopropyl Alcohol
Authors: Logsdon John E. , Loke Richard A.
Published: July 2004

Isopropyl alcohol is a colorless, volatile, flammable liquid having a low order of toxicity and a mild odor. Its main uses are as a chemical intermediate and in solvent applications in medicine and industry. The majority of the isopropyl alcohol in the United States is produced by indirect hydration of propylene in the weak sulfuric acid process. Outside the United States, several acid‐catalyzed direct hydration of propylene processes are also used. The indirect process can use refinery‐grade propylene streams and lower operating pressures than the direct process, but suffers from higher corrosion and maintenance costs. These processes and the various catalysts employed are described. Isopropyl alcohol demand in the United States has been declining slowly since 1983. Demand is expected to grow slightly owing to increasing use as a chemical intermediate. In addition to its use in the production of acetone, isoproyl alcohol is consumed in the production of higher ketones, amines, esters, and other chemicals. The use of diisopropyl ether as a fuel oxygenate may become a significant outlet for isopropyl alcohol.
Isoprene
Authors: Lybarger Hugh M.
Published: July 2004

Isoprene is a colorless, volatile liquid that is soluble in most hydrocarbons but is practically insoluble in water. Isoprene forms binary azeotropes with water, methanol, methylamine, acetonitrile, methyl formate, bromoethane, ethyl alcohol, methyl sulfide, acetone, propylene oxide, ethyl formate, isopropyl nitrate, methylal, ethyl ether, andn‐pentane. The exact conformation of the isoprene molecule is still in doubt. It generally is accepted that there is no free rotation around the central C–C single bond. Isoprene may be considered as an equilibrium of two conformations, namely a cisoid conformation in which both vinyl groups are located on the same side of the C–C bond, and the transoid one with the vinyl groups located on the opposite sides of the bond. Physical properties, polymerization, production, economic aspects, and health and safety factors are described.
Ketenes, Ketene Dimers, and Related Substances
Authors: Abaecherli Claudio , Miller Raimund J.
Published: July 2004

This article describes monomeric ketenes, ketene dimers, and acetoacetic acid derivatives. The parent substance, ketene itself, is the only ketene to be manufactured in large industrial quantities. The manufacturing process, chemical and physical properties, and industrial uses of ketene are described in detail. A table is included that lists examples of higher ketenes, thioketenes. The manufacture of acetic anhydride is described.

The article gives a thorough review of all aspects of diketene which is an important product derived from ketene on an industrial scale. Diketene gives access to open‐chain acetoacetic acid derivatives as well as heterocyclic systems. An overview is provided on dimeric aldoketenes and ketoketenes.

Acetoacetic acid derivatives are of significant economic importance. The manufacturing processes of diketene esters and of acetoacetarylides are outlined. This includes methyl acetoacetate and acetoacetanilide. Industrial uses of the various ketene and diketene derivatives are discussed with emphasis on the most important life science applications. Vol. 14, pp. 953–978, 157 refs. to December 1993.
Kinetic Measurements
Authors: Magde Doug
Published: July 2004

Kinetic measurements measure the rates of reactions. The information obtained is useful for fundamental understanding of chemical mechanism and for a variety of applications. The overall rate law for a reaction and the definition of associated rate constants must be consistent with the stoichiometric chemical equation for the reaction, but cannot be predicted from the stoichiometric equation alone. A detailed reaction scheme (or an even more descriptive reaction mechanism), which specifies any intermediates that occur in the reaction and describes exactly which atoms or molecules react in each elementary step, is needed to predict a rate law. The goal of kinetic measurements is to verify the functional form of the rate law and determine any constants in the rate law. The constants are quantities that do not vary when concentrations of reactants change; but they do vary with temperature, solvent, and other reaction conditions. Kinetic measurements involve preparing reactants at concentrations different from equilibrium values and then monitoring concentrations as they approach equilibrium. Simple manual mixing may suffice. More rapid reactions may be studied by flow‐mixing reactants in a moving stream or by injecting and mixing rapidly in a stopped‐flow device. Even faster reactions require perturbation techniques that start with a homogeneous mixture and perturb conditions away from equilibrium. This can be accomplished by changing external thermodynamic conditions such as temperature or pressure. Altematively, a reagent precursor may be switched suddenly to an active form by a flash of light (flash photolysis) or a pulse of electrons (pulse radiolysis). A host of reaction schemes are possible, but the Michaelis‐Menten scheme applicable to much enzyme catalysis receives special attention. The temperature dependence of rate constants is discussed in terms of an activation energy, and the dependence on pressure is characterized by an activation volume. Brief mention is made of recent progress in reaction dynamic studies, which provide in a few cases both experimental and theoretical treatments at the full quantum mechanical level.
Lanthanides
Authors: Leveque A. , Sabot J. L. , Maestro P.
Published: July 2004

Lanthanides is the name given collectively to the 15 elements from lanthanum to lutetium sharing the same space in Mendeleev's original Periodic Table. Lanthanides have a unique electronic structure because of partially filled 4forbitals. Occurrence and preparation of the rare earths is described. Mining of lanthanide ores and the various separation methods are discussed. Except for cerium and europium, the lanthanides are separated industrially of solvent extraction. The production of lanthanide metals is also presented.

Industrial applications of lanthanides encompass a number of different fields, including the high technology field of electronics. Uses in metallurgy, catalysis, and the glass and ceramics industry are based on unique chemical and structure properties. Uses as luminescent materials for phosphor applications or in medical imaging technology are limited to specific optical properties. Uses of lanthanides and their alloys as high energy magnets result from the special magnetic properties. Information storage is but one of many industries in which lanthanide usage is expected to grow. Vol. 14, pp. 1091–1116, 51 refs. to January 1993.
Lead Compounds
Authors: Carr Dodd S. , Spangenberg William C. , Chronley Kevin , Meshri Dayal T.
Published: July 2004

All lead‐containing compounds are produced from pig lead through a series of steps, except for the small amount of lead in leaded zinc oxide for which high grade lead ore is used. Most lead compounds are prepared directly or indirectly from lead monoxide, commonly known as litharge.

About 80% of the lead in the United States is allocated to use in batteries supplied as either a mixed oxide or as metal. Lead is also consumed in the production of plastics, gasoline additives, rubber, ceramics, glass, and electronics. Physical properties and health and safety factors, as well as OSHA and EPA regulations, are given.
Lead
Authors: King Michael , Ramachandran Venkoba
Published: July 2004

On a weight basis lead is the fifth most used metal in the world. As a metal, lead is prized for properties such as high density, ease of fabrication, chemical stability in air and water, ability to absorb high energy radiation, and for its electrochemistry, especially the reaction with sulfuric acid. The lead–acid storage battery is used worldwide. Lead also forms alloys and compounds.

Lead is generally recovered from ores containing 2–6% lead sulfide. After concentration, the sulfide is smelted to metal, refined to remove impurities, and the valuable by‐products such as silver and gold recovered. Several newer technologies for smelting have come into commercial operation outside of the United States to replace the traditional sinter/blast furnace process. Refining and by‐product recovery are achieved by traditional pyrometallurgical and electrolytic methods. These primary production methods are described.

Recycling of the lead in scrap lead–acid batteries is steadily increasing and, in the United States, accounts for two‐thirds of the lead consumed annually. Secondary production methods are described, including technologies under development to improve recycling capabilities.

World consumption of lead has increased despite environmental concerns of health and safety factors. Future growth in the lead industry, however, depends on the market for lead–acid batteries.
Lecithin
Authors: Wendel Armin
Published: July 2004

Lecithins and phospholipids occur in all living organisms. They are components of biological membranes. Commercial lecithins are by‐products of the industrial production of vegetable oils. They are referred to as soya, sunflower, rape lecithin, etc, depending on their origins. The most important of these preparations is soya lecithin, so the term lecithin almost always refers to this.

Commercial lecithins are mixtures. They are made up of ca 50% phospholipids, ca 10% carbohydrates and glycolipids, and of ca 40% triglycerides, free fatty acids, sterols, and other minor components of vegetable oils. The significant components are the phospholipids, whose surface‐active properties endow the lecithins with their unique position as emulsifier and dispersants. Because they are permitted in foodstuffs throughout the world without limitations, they find their broadest application in food. Native, ie, unprocessed, lecithins have also been found useful as additives to animal feed and in technical products.

Fractionation or chemical modification of lecithins yields preparations with improved activity or with a wider range of application. The surfactant and wetting properties of vegetable lecithins are improved by acetylation, hydroxylation, and partial hydrolysis. Hydrogenation improves the resistance to oxidation and aging and increases the water‐binding capacity of the preparation. In spite of the multiplicity of possible applications only about 10% of the available lecithin is produced (ca 130,000 t).
Licensing
Authors: Ku Katharine
Published: July 2004

A license is an agreement which conveys specified patent, copyright, trademark, or know‐how rights from one party to another. The main terms and conditions of a license generally include diligence provisions, financial obligations, and a conveyance of the rights exclusively or nonexclusively. The considerations in valuing a technology are discussed. Licensing is usually a business arrangement for the mutual benefit of the parties and should be part of an overall commercialization and business strategy.
Light‐Emitting Diodes
Authors: Kish Fred
Published: July 2004

Light Generation (Light‐emitting diodes). The light‐emitting diode (LED) is one of the most technologically fundamental and commercially important of compound semiconductor devices. Such emitters consist of a
p
–
n
junction diode formed in compound semiconductor material that emits radiation in the ultraviolet, visible, or infrared in response to an electrical current passing through a forward‐biased device. Radiative recombination in these devices is strongly influenced by a variety of material and structural properties, including the nature of the energy gap of the semiconductor and the presence of impurities or defects in the device. An important challenge in these devices is the ability to extract light from the high index semiconductor material into the outside world. Generally, LEDs may be grouped into two categories depending on performance and application. Visible or display emitters are utilized in lighting applications, and communications LEDs (mostly infrared) are utilized to optically transmit data. The various optoelectronic components, materials systems, and types of layered structures and dopants are discussed. Device design, fabrication techniques, and performance and presented.
Lignin
Authors: Lebo Stuart E. , Gargulak Jerry D. , McNally Timothy J.
Published: July 2004

The word lignin is derived from the latin wordlignummeaning wood. It is one of the main components of all vascular plants and the second most abundant polymer in nature. This article describes the current understanding of the structure of this complex natural polymer. The number and types of different chemical bonds present in lignin are discussed as are the ways in which different lignins are identified and their distributions determined in plant tissues. Means for isolating lignin from wood are described, and the chemical and physical properties of the resulting lignins are reviewed. The various chemical and instrumental methods for characterizing isolated lignins are also discussed. This article concludes with a review of commercial lignin products including a discussion of producers, production methods, modification reactions, and the many industries in which lignins are used.
Lignite and Brown Coal
Authors: Vorres Karl S.
Published: July 2004

Lignite and brown coal are intermediate between peat and bituminous coal. These coals are high in moisture content, low in density, and frequently low in sulfur, and tend toward spontaneous ignition in air. The brown coals are geologically younger than the firmer, fibrous lignite. Deposits, from 2–60 million years old, are found mainly in Russia, central Europe, Australia, and the United States. Proved reserves, about 300 billion metric tons, represent close to a 290 year supply at 1990 production rates.

Most lignite and brown coal is burned for electric power generation and mines are usually close to utilization sites for both economic and safety reasons. Lignite briquettes are also used for domestic heating in various parts of the world. Processes for lignite and brown coal conversion to synthesis gas for feedstock utilization, to both gaseous and liquid fuels, and to materials for use as soil conditioners, wax, and so on, are described.
Lincosaminides
Authors: Bannister Brian
Published: July 2004

Lincomycin, C18H34N2O6S, the first lincosaminide antibiotic to which a structure was assigned, is defined chemically as methyl 6,8‐dideoxy‐6‐(1‐methyl‐trans‐4‐propyl‐L‐pyrrolidin‐2‐ylcarbonylamino)‐1‐thio‐D‐erythro‐D‐galacto‐octopyranoside. Both lincomycin and the semisynthetic clindamycin, C18H33ClN2O5S, are widely used in clinical practice. The trivial name of the sugar fragment of this antibiotic, methyl α‐thiolincosaminide, has lent itself to the other members of this family. Lincomycin has been produced by a variety ofStreptomycesstrains and by strain 1146 ofActinomyces roseolus.The earliest studies on the mechanism of action of lincomycin showed that lincomycin had the immediate effect onStaphylococcus aureusof complete inhibition of protein synthesis. Little effect on DNA and RNA synthesis was observed. Resistance to lincomycin is developed slowly, and leads to coresistance to macrolide, lincosaminide, and streptogramin B antibiotics. Lincomycin hydrochloride (Lincocin) is available in oral dosage forms and as a sterile solution for injection. Lincomycin has found use in the treatment of diseases of the ear, throat, nose, respiratory tissue, skin and soft tissue, bone, joint, dental, and septicemic infections caused by staphylococci, pneumonococci, and streptococci (other than enterococci). It has also been used in the treatment of diphtheria. Clindamycin, 7(S)‐7‐chloro‐7‐deoxylincomyin, also known as Cleocin, first resulted from the reaction of lincomycin and thionyl chloride; improved synthetic methods involve the reaction of lincomycin and triphenylphosphine dichloride or triphenylphosphine in carbon tetrachloride. Clindamycin is significantly more active than lincomycin against gram‐positive bacteriain vitro,and is absorbed rapidly following oral administration. Clindamycin has found use in the treatment of common infections caused by gram‐positive cocci. It is also efficacious in the treatment of anaerobic infections, including actinomycosis. Clindamycin has been shown to be active against strains ofPlasmodiumin animals. Cross‐resistance between lincomycin and clindamycin is complete, and co‐resistances of lincomycin also apply to clindamycin. The composition of matter patents in the United States issued to The Upjohn Company on clindamycin phosphate and hydrochloride having expired at the end of 1986 and in early 1987, respectively, these compounds have been available generically from more than two dozen companies in the United States alone.
Coal Conversion Processes Liquefaction
Authors: Dadyburjor Dady B. , Liu Zhenyu
Published: July 2004

Coal liquefaction incorporates both an increase in the H/C ratio and removal of heteroatoms (S, N, O) and inorganic oxides (ash). Successful industrial processes must incorporate both these steps along with the transport of solid‐ and slurry‐phase material in large‐scale processing. The H/C ratio can be increased using high temperatures and pressures and a solvent (generally process derived), or by a catalyst, or by heating rapidly in the absence of a solvent in hydrogen or an inert atmosphere. Sometimes there are advantages to processing coal simultaneously with other fossil fuels such as resids. Typically, such operations, termed coprocessing, result in improved removal of heteroatoms and ash. The use of solids and slurries has resulted in novel reactors and processing steps. Fuel production can be direct, from the coal itself, or indirect, from synthesis gas (CO and H2) obtained by gasification of the coal. Synthesis gas, in particular, can be used to produce chemicals other than fuels. The production of these chemicals often can be used to make favorable the economics of fuel production from coal.
Liquid Level Measurement
Authors: Boisvert Jerry , Carsella Boyce , Shannon Wayne , Williams Ted
Published: July 2004

Liquid level measurement is considered one of the four primary process measurement parameters, ie, temperature, pressure, flow, and level. Measurement of any of the parameters is difficult due to the harsh conditions present in many processes. High temperature, high pressure, corrosive environments, turbulence, etc, are a few of the conditions a measurement device must endure if it is to fulfill its goal of accuracy and dependability. Due to these factors, numerous and various level measurement devices have been developed to effectively handle particular types of applications.

The following approaches are covered in the article: sight glasses, dip stick, magnetic liquid level indicators, floats, displacers, buoyancy, conductivity, capacitance, pressure/differential pressure, ultrasonic, microwave, fiber optic, thermal disposition, magnetostrictive, phase tracking, servo gauge, and radiation.