bluuebunny/crossref_metadata_2025 huggingface dataset:
Drug Delivery Systems
Authors: Quadros Elizabeth , Comfort Ann R. , Dinh Steven M. , Berner Bret
Published: August 2004

The concepts of drug delivery are described, focusing on the application of polymer chemistry to design a well‐characterized controlled dosage form that produces the desired drug delivery profile. In order to design a system, both drug release from the system, ie, desorption or dissolution, and absorption across the relevant biological membrane are measured. The physiology and barrier properties of different routes of drug delivery, which include oral, rectal, transdermal, buccal, nasal, pulmonary, ocular, and vaginal, are described. The mechanisms that govern drug release from systems include diffusion (including osmotic), chemical, swelling, and external control, such as iontophoresis or electromechanical devices. Examples are given of commercially available systems from each class, including implants, oral osmotic devices, transdermal and ocular systems, and infusion pumps. Characterization of the physical and chemical properties of the system components is described, as well as the different types of manufacturing processes and characterization of the final system, including drug release and adhesion, if relevant.
Dyes, Environmental Chemistry
Authors: Reife Abraham
Published: August 2004

Synthetic organic dyes are essential to satisfy the ever growing demands in terms of quality, variety, fastness, and other technical requirements for coloration of a growing number of substances. Beginning in 1970, however, the dyestuff and textile industries have become increasingly subject to international, federal, and state regulations designed to improve health, safety, and environment. Therefore, in an attempt to provide a perspective of the environmental problems posed by synthetic organic colorants, and the efforts being made by industry, academia, and government to solve these problems, this article includes the physical, chemical, and biological methods of effluent treatment of dye wastewater. Specifically, the physical methods are adsorption, sedimentation, flotation, flocculation, coagulation, foam fractionation, polymer flocculation, reverse osmosis and ultrafiltration, ionization radiation, and incineration; the chemical methods are neutralization, reduction, oxidation, electrolysis, ion exchange, and wet air oxidation; the biological methods are stabilization ponds, aerated lagoons, trickling filters, activated sludge, anaerobic digestion, and bioaugmentation. Also included are fate of dyes, analytical methods, pollution prevention, heavy metals, toxicity, and legislation.
Dyes, Reactive
Authors: Smith Roy E.
Published: August 2004

Reactive dyes are those dyes that are electrophilic and react with a nucleophilic group of a substrate to form a covalent chemical bond. They offer improved washfastness over dyes that are mechanically entrapped by the substrate. Brighter shades can be obtained on cellulose with reactive dyes than with large molecular weight direct dyes.

Reactive dyes for cellulose were first commercialized by ICI in 1956 under the trade name Procion M. The reactive group of those dyes was dichlorotriazine. Since that time more than 40 reactive groups have been reported. However, the most important groups for cellulose are monochlorotriazine, vinyl sulfone, and monofluorotriazine, in order of increasing reactivity. Acrylamide andα‐bromoacrylamide are the most important reactive groups for wool where usage is minimal compared to cellulose. Difunctional reactive dyes with functional groups of different reactivity were commercialized in the early 1980s, and gave much greater substantivity on cellulose than had previously been possible.

Since about 1980 reactive dyes have represented the principal research and development efforts among the several classes of textile dyes. Most efforts are directed toward improved dye fixation on the substrate to minimize ecological adversities and improve economics. The most common approach to achieve this objective is the use of bifunctional dyes, which may be applied over a wide range of reaction conditions. Reactivity may be varied by selection of reactive group, or by inductive effects of the dye chromophore on the reactive group.
Dyes, Sensitizing
Authors: Sturmer David M.
Published: August 2004

Spectral sensitizing dyes enhance the colors and wavelengths to which photosensitive systems respond. Color photography requires spectral sensitizers for each of the color regions of the visible spectrum (blue, green, and red). Infrared spectral sensitizers are essential to a wide variety of processes, including infrared photography, electrophotography, and optical disk data storage. Chlorophyll is the natural sensitizer in plants, and retinal derivatives activate our vision system. Other spectral sensitizers find specialty uses in photoresists, solid‐state laser‐activated printing, graphic arts/x‐ray films, manufacture of perfume constituents, and photochemical disease therapy.
Economic Evaluation
Authors: Ward Thomas J.
Published: August 2004

Economic evaluation is the financial assessment of a proposed venture, relative to other possible choices. Problem definition is the first part of economic evaluation. Cost estimation involves equipment, capital investment, and product cost. Revenue estimation considers product price and factor estimates. Profitability analysis utilizes multiyear process ventures, ie, money flows of capital investments, sales revenues, annual cash flow, etc; and profitability criteria, ie, net present value, discounted total capital, internal return rate, etc. Cash flow examples are included, as are profitability and sensitivity diagrams. Break‐even charts, inflationary effects, and statistical analysis are also discussed.
Electroplating
Authors: Horner Jack
Published: August 2004

Electroplating is a diversified industry using a variety of metals and alloys to plate on many base materials for a wide range of both decorative and functional applications. Whereas the majority of substrates are metals and alloys, there are a large and growing number of plastics being plated. More electroplated materials are used for their functional properties than for their decorative ones.

The fundamentals of the electroplating process, cleaning and preparation of the base materials, bath formulations, operating conditions, and the properties of the electroplated deposits are presented. The overall environmental impact of the industry is discussed with an eye to waste management. Changes in the electroplating industry, such as the increased use of trivalent chromium and zinc alloys, are being environmentally driven.
Electrically Conductive Polymers
Authors: Reynolds John R. , Child Andrew D. , Gieselman Melinda B.
Published: August 2004

An overview of the field of electrically conductive polymers is presented. The synthesis of conducting polymers is discussed with detailed sections describing polyacetylenes, polyphenylenes, polyheterocycles, poly(arylene vinylenes), and polyanilines. The preparations of conducting polymer blends, composites, and colloids are described. The concept of redox doping to form charge carriers on conjugated polymers and its effect on optical and electrical properties is given. The effect of polymer structure on electronic properties is demonstrated. The stabilities of conducting polymers are compared. A number of applications are outlined; these include charge storage batteries, conductive textiles, chemical biochemical sensors, electromagnetic shielding, antistatic coatings, gas separation membranes, electrochromism, and electroluminescence.
Emulsions
Authors: Friberg Stig E. , Jones Steven
Published: August 2004

The formation, stability, and applications of emulsions are reviewed with the focus on more complex systems than the traditional two‐phase liquid‐in‐liquid dispersions. The presence of a third phase is demonstrated to change the properties of the emulsion in a significant manner and is, in fact, in some cases a necessity for specific applications.
Enzyme Inhibitors
Authors: Muscate Angelika , Levinson Cynthia L. , Kenyon George L.
Published: August 2004

Modern approaches to rational drug discovery have led to a number of different strategies for the design of enzyme active‐site directed inhibitors, which can be divided into classes describing noncovalent and covalent binding. Noncovalently binding inhibitors can be subdivided into rapidly reversible, tight, slow, slow‐tight binding inhibitors, transition‐state, and multisubstrate analogues. Covalently binding inhibitors are grouped into mechanism‐based inhibitors, affinity labels, and pseudoirreversible inhibitors. Inhibitors that fall into one or more of these categories have been designed using mechanistic and structural information. Computer‐aided drug design has been used as a new and powerful approach for the design of inhibitors. Using three‐dimensional enzyme structures or pharmacophores, novel, nonsubstrate analogue lead compounds have been developed byde novodesign or screening of small molecule databases and further optimized to obtain potent inhibitors. Alternatively, quantitative structure‐activity relationship methods (QSAR), comparative molecular field analysis (CoMFA), or perturbation free‐energy calculations have used the speed and computational power of computer algorithms to establish structure‐activity relationships for a series of structurally related compounds, allowing for the design of more potent inhibitors.
Ethanol
Authors: Logsdon John E.
Published: August 2004

Ethanol's unique combination of physical and chemical properties has led to its use as a solvent, a germicide, a beverage, an antifreeze, a fuel, a depressant, and a chemical intermediate for other organic chemicals. Most industrial ethanol is produced from ethylene by the direct hydration process. Ethanol from fermentation processes is the second most important source. The subsidized (federal and state) use of fermentation ethanol in gasoline has fueled a rapid growth in U.S. production, which has provided some ethanol for crossover to the industrial market. The 1990 Clean Air Act requiring the use of oxygenates in gasoline has further fueled this growth. Corn is the principal feedstock for fermentation in the United States, and sugar cane is the most important raw material outside the United States. This rapid growth has also caused a renewed interest in research into this ancient process. The main uses for industrial ethanol are as an intermediate for the production of other chemicals and as a solvent. The United States Treasury, Bureau of Alcohol, Tobacco, and Firearms oversees the production, procurement, and use of ethanol in the United States.
Ethyl Chloride
Authors: Miller Matt C.
Published: August 2004

Ethyl chloride (chloroethane), C2H5Cl, is a colorless, mobile liquid with a nonirritating ethereal odor and a pleasant taste. It is flammable, is normally stored as liquefied gas, and burns with a green‐edged flame, producing hydrogen chloride fumes. This article discusses its properties, manufacture, toxicology, and economic aspects. Ethyl chloride has primarily been used in the manufacture of the fuel additive tetraethyllead (TEL). Environmental legislation mandating the use of lead‐free fuels has caused a steep decline in production of ethyl chloride. A recent study has shown evidence of carcinogenic activity in female mice exposed to 15,000 ppm. The only other important demand for ethyl chloride is in the production of ethylcellulose.
Ethylene–Propylene–Diene Rubber
Authors: Noordermeer Jacobus W. M.
Published: August 2004

EPM and EPDM are the fastest growing elastomers by virtue of their excellent ozone resistnce in comparison with commodity rubbers. Even though these rubbers have been commercially available for more than 30 years, the production and applications technologies are still very much under development. The various structural parameters of EP(D)M are described, as well as how these depend on production conditions. EP(D)M is produced in suspension with liquid propylene as dispersing agent, or most commonly in solution where the polymer produced is dissolved in a hydrocarbon solvent. The solution process technology is described in detail. EP(D)M can be compounded with fillers and plasticizers. Basic principles of compounding are described, including a few typical examples of EP(D)M recipes. EP(D)M can be mixed, extruded, and vulcanized on all common rubber‐factory equipment.

The mechanical properties depend considerably on the structural characteristics of the EP(D)M and the type and amount of fillers in the compound. Some typical properties of EP(D)M vulcanizates are good elastic properties, resistance to heat and ozone, various chemicals, and good electrical properties. The principal uses of vulcanized EP(D)M rubber are in automotive, building and construction, cable and wire, and appliances. Unvulcanized EP(D)M rubber is mainly used in blends with thermoplastics, particularly polypropylene, and as an oil additive.
Ethylene
Authors: Sundaram K. M. , Shreehan M. M. , Olszewski E. F.
Published: August 2004

In this comprehensive discussion of the production of and uses for ethylene, the topics covered include the properties of ethylene; industrial production; storage, shipping, handling; and economics. Extensive coverage of the commercial production of ethylene via thermal cracking is provided. The reaction is discussed as well as the methods employed to predict the feedstock conversion. Product distributions are given for a variety of feedstocks. A description of the industrial furnaces available is given, as well as a typical process description and process flow diagram. Information is provided on coke deposition during the cracking process, giving the methods used to inhibit coke production and methods used to remove coke deposited. Recent improvements in the design of ethylene plants plus possible other routes to produce ethylene are presented.
Ferrites
Authors: Kools F. X. N. M. , Stoppels D.
Published: August 2004

Two main groups of commercial ferrites are emphasized; the soft magnetic spinel ferrites having as the most important representatives MnZn‐, NiZn, and MgZn‐ferrites; and the hard magnetic hexagonalM‐type ferrites having as the main representatives BaM‐ and SrM‐ferrites. These materials are primarily ceramics. The cubic spinel and the hexagonalM‐type crystal structures produce differing magnetic and electrical properties, which result from electron configurations and mutual interactions of the constituent ions. Properties can be optimized for specific applications in the areas of consumer electronics, telecommunication, power conversion, and the automotive industry. Optimum ceramic processing, often including microstructural engineering, is required to obtain fine‐tunings of the various parameters for ferrite applications.
Fiber Optics
Authors: Kosinski Sandra , MacChesney John B.
Published: August 2004

Fiber‐optic based communication depends on the availability of high quality low loss optical fibers. Light guidance within a fiber is discussed.

Operating wavelengths have been extended by controlling fiber attenuation and dispersion. Fiber fabrication methods are presented. The use of high purity starting materials and vapor deposition techniques allows the production of glass fibers having optical losses that approach the intrinsic loss of silica. Fiber drawing processes determine strength. Active optical fibers have been exploited to amplify light, extending the range of transmission systems and allowing increased capacity. Erbium‐doped fibers are being used for signal amplification in fiber‐optic cable. Devices taking advantage of gratings written in optical fibers include filters and lasers. The market for fiber‐optics materials is expected to continue to grow.
Filtration
Authors: Svarovsky Ladislav
Published: August 2004

This article defines and reviews the field of filtration, with a particular emphasis on cake filtration of liquids as the most dominant unit operation in the field. The necessary definitions are given and are followed by a discussion of operations closely related to or used in conjunction with filtration. A brief account of cake filtration theory is followed by descriptions of available individual groups of filtration technology.

A section on vacuum filters discusses the nutsche filter, enclosed agitated vacuum filters, vacuum leaf filters, tipping pan filters, horizontal rotating pan filters, horizontal belt vacuum filters, rotary vacuum drum filters, and rotary vacuum disk filters. The very large field of pressure filtration is subdivided into batch and continuous filters. Batch pressure filters include filter presses, pressure vessel filters, cartridge filters, and batch compression filters; continuous pressure filters include disk filters, drum filters, horizontal belt pressure filters, continuous compression filters (belt presses and screw presses), and thickening pressure filters (including cross‐flow filtration and dynamic filters). A separate section on centrifugal filters deals with fixed‐bed centrifuges and moving bed centrifuges.
Fuel Cells
Authors: Kinoshita Kimio , Cairns Elton J.
Published: August 2004

Fuel Cells.
Fuel cells are electrochemical devices that convert the chemical energy of a fuel directly into electrical and thermal energy. In a typical fuel cell, gaseous fuels are fed continuously to the anode (negative electrode) compartment, and an oxidant, eg, oxygen or air, is fed continuously to the cathode (positive electrode) compartment. The electrochemical reactions take place at the electrodes to produce an electric (direct) current. The fuel cell theoretically has the capability of producing electrical energy for as long as the fuel and oxidant are fed to the electrodes. In reality, degradation or malfunction of components limits the practical operating life of fuel cells.

Besides the direct production of electricity, heat is also produced in fuel cells. This heat can be effectively utilized for the generation of additional electricity or for other purposes, depending on the temperature. A practical consideration for fuel cells is compatibility with the available fuels and oxidants. One of the main attractive features of fuel cell systems is the expected high fuel‐to‐electricity efficiency. This efficiency, which runs from 40–60% based on the lower heating value (LHV) of the fuel, is higher than that of almost all other energy conversion systems. The two primary impediments to the widespread use of fuel cells are high initial cost and short operational lifetime. A variety of fuel cells has been developed for terrestrial and space applications. Fuel cells are usually classified according to the type of electrolyte used in the cells as polymer electrolyte fuel cell (PEFC), alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), and solid oxide fuel cell (SOFC).

Fuel cells operating on pure H
2
and O
2
provide a useful power source in remote areas such as in space or under the sea where system weight and volume are important parameters. On the other hand, fuel cell power plants operating on fossil fuels and air offer the potential for environmentally acceptable, highly efficient, and low cost power generation. The minimum technical requirements for fuel cells for four different types of applications, ie, for buildings, industry, transportation, and utilities are given. From the standpoint of commercialization of fuel cell technologies, there are two challenges: initial cost and reliable life.

Several activities, would strongly boost the prospects for fuel cell technology and include the development of
(1)
an active electrocatalyst for the direct electrochemical oxidation of methanol;
(2)
improved electrocatalysts for oxygen reduction; and
(3)
a more CO‐tolerant electrocatalyst for hydrogen.
Gas, Natural
Authors: Woodcock Kermit E. , Gottlieb Myron
Published: August 2004

Natural gas is a mixture of naturally occurring hydrocarbon and non‐hydrocarbon gases found in porous geologic formations beneath the earth's surface. Methane is a principal constituent and the mixture may contain higher hydrocarbons such as ethane, propane, butane, and pentane. Gases such as carbon dioxide, nitrogen, hydrogen sulfide, various mercaptans, and water vapor along with trace amounts of other inorganic and organic compounds can also be present. Natural gas is found in a variety of geological formations including sandstones, shales, and coals. Worldwide natural gas reserves have continued to increase as the demand for gas has increased and exploration efforts have expanded. Natural gas production on a worldwide basis has also continued to increase. The composition of natural gas at the wellhead depends on the characteristics of the reservoir and is highly variable with respect to both the constituents present and the concentrations of these constituents. Natural gas obtained at the wellhead usually undergoes some type of treatment or processing prior to its use for safety, economic, or system and material compatibility reasons. Gases are odorless, but for safety reasons, natural gas is odorized before distribution to provide a distinct odor to warn users of possible gas leaks in equipment.

Natural gas is used as a fuel and source of heat throughout the industrialized countries for a broad range of residential, commercial. Both natural gas and natural gas liquids are used as feedstocks in the chemical industry. Production takes place both at onshore installations and on offshore platforms which service wells drilled to provide access to reservoirs located below the floor of the ocean.
Glass‐Ceramics
Authors: Pinckney Linda R.
Published: August 2004

Glass‐ceramics are polycrystalline materials formed by the controlled crystallization of glass. Most commercial glass‐ceramic products are formed by highly automated glass‐forming processes and converted to a crystalline product by the proper heat treatment. Glass‐ceramics can also be prepared via powder processing methods in which glass frits are sintered and crystallized. The range of potential glass‐ceramic compositions is therefore extremely broad, requiring only the ability to form a glass and control its crystallization.

Glass‐ceramics can provide significant advantages over conventional glass or ceramic materials, by combining the ease and flexibility of forming and inspection of glass with improved and often unique physical properties in the glass‐ceramic. Their physical properties are highly reproducible.

Unlike conventional ceramic materials, glass‐ceramics are fully densified with zero porosity. They generally are at least 50% crystalline by volume and often are greater than 90% crystalline.

More than $500 million in glass‐ceramic products are sold yearly worldwide. These range from transparent, zero‐expansion materials with excellent optical properties and thermal shock resistance to jade‐like highly crystalline materials with excellent strength and toughness. The highest volume is in cookware and tableware, architectural cladding, and stovetops and stove windows. Glass‐ceramics are also referred to as Pyrocerams, vitrocerams, devitrocerams, sitalls, slagceramics, melt‐formed ceramics, and devitrifying frits.
Gold and Gold Compounds
Authors: Cohn J. G. , Stern Eric W.
Published: August 2004

Gold is characterized by high density, high electrical and thermal conductivities, and high ductility. At least 26 unstable gold isotopes have been made.

Gold is the most noble of the noble metals. Other than in the atomic state, the metal does not react with oxygen, sulfur, or selenium at any temperature. It does, however, react with tellurium at elevated temperatures to produce gold ditelluride which is also found in the naturally occurring mineral, calaverite. Gold reacts with the halogens, particularly in the presence of moisture.

Gold reacts with various oxidizing agents at ambient temperatures provided a good ligand is present to lower the redox potential below that of water. Thus, gold is not attacked by most acids under ordinary conditions and is stable in basic media. Gold does, however, dissolve readily aqua regia and in alkaline cyanide solutions in the presence of air or hydrogen peroxide to form (Au(CN)2)−. These reactions are important to the extraction and refining of the metal. Gold is very corrosion and tarnish resistant and imparts corrosion resistance to most of the commonly used gold alloys.

Placer mining is the oldest form of gold mining. The technique is still in use in places where appropriate alluvial or marine deposits exist, such as Alaska, but requires large quantities of water. At present, most gold is obtained either by deep mining, most notably in South Africa, or by open pit mining such as in the United States. In refining precious metal scrap and some concentrates, the gold is converted to HAuCl4by treatment with aqua regia. After heating to remove nitrogen oxides, gold is precipitated from solution by reduction with sulfur dioxide or ferrous sulfate. Gold is widely distributed and the average content in the earth's crust is estimated to be 3.5 ppb. The gold content of ocean water varies considerably with location. The average value is of the order of 10 ppt, which is well below the concentration (3 ppm) required for economic recovery.

Chrysotherapy, therapy with gold compounds, remains as one of the few treatments capable of slowing or halting the damage caused by rheumatoid arthritis. Besides its use for monetary reserves, gold is used in the private sector principally for investment and fabrication. By far, the largest commercial use is jewelry. In the electronics industry, gold is used as fine wires or thin film coatings and frequently in the form of alloys to economize on gold consumption and to impart properties such as hardness.

In dentistry, gold is used for a variety of restorations.

The chemistry of nonmetallic gold is predominantly that of Au(I) and Au(III) compounds and complexes.

Common gold compounds include halides, cyanides, oxides and hydroxides hydroxide, Au(OH)3), and sulfides. Both alkyl and aryl complexes of Au(I) and Au(III) as well as olefin and acetylene complexes have been prepared and studied. An increasing amount of interest has developed in gold‐containing bimetallic cluster compounds.
Hydrides
Authors: Sullivan Edward A.
Published: August 2004

Sullivan, Edward A. (Morton International). Hydrides may be divided into two groups: simple and complex. The simple or binary hydrides may be ionic, covalent, or interstitial as are most of the transition metal hydrides. The important properties, methods of manufacture, safe handling, and important uses of the commercial binary hydrides and certain hydrogen storage alloys are reviewed. Alkali metal, alkaline‐earth, and Group 4, 5, 13, and 14 hydrides find use in a variety of industries among which are the electronics, pulp and paper, dyeing, and clay industries.

The most important complex hydrides are the borohydrides and alumino‐hydrides. The important alkali metal salts of these hydrides are described. Complex hydrides are used principally in the synthesis of organic compounds effecting specific and nonspecific reductions. Alkoxyborohydrides, cyanoborohydride, acyloxyborohydrides, and alkoxy‐aluminohydrides, are also discussed.
Carbides, Industrial Hard
Authors: Stoll W. M. , Santhanam A. T.
Published: August 2004

The four most important carbides for the production of hard metals are tungsten carbide, WC, titanium carbide, TiC, tantalum carbide, TiC, and niobium carbide, NbC. The binary and ternary solid solutions of these carbides such as WC–TiC and WC–TiC–TaC (NbC) are also of great importance. Carbides and their solid solutions are generally combined with cobalt and used in the form of cemented carbides. The carbides of the actinides, Th, U, Pu, and Np, have gained importance in reactor technology as nuclear fuels. In general, the carbides of metals of Groups 4–6 (IVB–VIB) are prepared by reaction of elementary carbon or hydrocarbons and metals and metal compounds at high temperatures. Methods include carburization by fusion, carburization by thermal diffusion, carburization by menstruum process, carburization by thermochemical reaction, and reduction. Two categories of refining support manufacturers of cemented carbides. The first involves extraction of tungsten in the form of tungstic oxide, WO3, or ammonium paratungstate APT, from mineral concentrates. The second converts the APT and other starting materials to primary carbides of tungsten and other metals. Some refining is carried out by the cemented carbide manufacturers themselves. Cemented carbide manufacturers also utilize independent refiners. A number of cemented carbide producers market some or all primary materials, ranging from monocarbides to binary or ternary solid solutions involving TiC, TaC, NbC, or WC.
Peroxides and Peroxide Compounds, Inorganic Peroxides
Authors: Comyns Alan E.
Published: August 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 bleaching, polymerization catalysts, dough‐conditioning, effluent treatment, pyrotechnics, as well as uses in medicines, household detergents, hydrometallurgy, and organic synthesis.
Titanium Compounds, Inorganic
Authors: Egerton Terry A.
Published: August 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 & safety aspects are summarized.
Cellulose Esters, Inorganic Esters
Authors: Fengl Richard
Published: August 2004

Cellulose esters are cellulose derivatives which result from the esterification of the free hydroxyl groups of cellulose with one or more acids. Cellulose nitrate is the oldest cellulose derivative and the only inorganic ester of commercial importance. Manufacturing and uses of sulfur‐ and phosphorus containing cellulose esters are discussed. An analysis of the oldest and most important inorganic ester of cellulose, cellulose nitrate, is presented.
Fluorine compounds, Organic, Introduction
Authors: Bajzer William X. , Kim Yung K.
Published: August 2004

Organic compounds bearing fluorine substituents are commercially important in many applications. The refrigerant application is over six decades old and continues to receive wide global attention due to the environmental impact of the chlorofluorocarbon (CFC) materials. Alternative hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC) materials are under development to replace the CFCs. The properties of many fluorinated organic compounds are contrasted with their hydrocarbon analogues. Various methods are described for introduction of fluorine singly or multiply into organic compounds. Attention is focused on the recommended commercial method to manufacture many fluorinated organic compounds. Fluorinated compounds are discussed by class, with examples given for each. Global production patterns and capacity by company are reviewed along with significant commercial trends. Toxicology of this class of materials is addressed from a brief overview perspective. Bibliographic references and suggestions for general reading are listed.
Iodine and Iodine Compounds
Authors: Lauterbach Armin , Ober Gustavo
Published: August 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.
Kinetic Measurements
Authors: Magde Douglas
Published: August 2004

Magde, Douglas (University of California at San Diego). The goal of kinetic measurements, which determine the rate of chemical changes, is to determine the form of a rate law. This law relates rates to reactant concentrations and one or more rate constants which remain unchanged as long as thermodynamic conditions are fixed. Measurements may be made by mixing components and measuring concentration changes over time. Methods, including stopped‐flow and continuous flow mixing for millisecond times, have been introduced to study reactions too fast for manual approaches. Faster reactions require perturbation methods employing temperature, pressure (including sound), and electrical field strength. Flash photolysis, also a perturbation, uses lasers to measure chemical or physical changes taking place in less than

\documentclass{article}\pagestyle{empty}\begin{document}${10^{-13}}$\end{document}

s. Other perturbation methods can approach

\documentclass{article}\pagestyle{empty}\begin{document}${10^{-9}}$\end{document}

s. Besides direct measurements of changing concentrations, kinetic studies can exploit linewidth measurements in optical spectroscopy and magnetic resonance. All these measurements of macroscopic behavior are then interpreted at the microscopic, atomic level in terms of mechanisms. The combination of increasingly detailed, fast measurements of primary processes and sophisticated computer modeling is starting to generate rigorous atomic level descriptions of kinetic change. Vol. 14, pp. 1021–1044, 16 refs. to December 1993.
Lead Salts
Authors: Carr Dodd S. , Spangenberg William C. , Chronley Kevin
Published: August 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.

As of the 1990s over half 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.
Methylene Chloride
Authors: Holbrook Michael T.
Published: August 2004

Methylene chloride is a colorless, heavy liquid with a pleasant ethereal odor. Its outstanding solvent properties are the basis of its principal industrial interest. It is produced almost exclusively by the chlorination of lesser chlorinated methanes along with coproducts chloroform and carbon tetrachloride. U.S. capacity has been estimated at 265,000 t/yr although there is considerable flexibility to change the mix of the coproducts made. Methylene chloride production has declined significantly since 1985 because of an unfavorable carcinogenicity test. Projected growth rates of

to

per year are typical for the early 1990s. Its primary uses are for paint stripping and metal cleaning. It is regulated by many federal and state laws.
Microscopy
Authors: McCrone Walter C.
Published: August 2004

Microscopy involves the production and study of magnified images of objects too small to resolve with the unaided eye. There is no single microscope; rather, there are dozens of types, having in common only the ability to present an enlarged image. Microscopes vary in the mechanism by which enlarged images are formed, and in the information presented for each enlarged object. Some microscopes use visible light; others use infrared, ultraviolet, or x‐ray radiation; electrons are also used. There are a variety of scanning microscopes, some of which scan the object with an electron beam, a laser beam, or ultraviolet light. Most recently, an entire family of microscopes have been developed that scan a surface, maintaining a constant, tiny distance from that surface and thus plotting a surface map of objects as small as single atoms.

Microscopes are also classified by the type of information they present: size, shape, transparency, crystallinity, color, anisotropy, refractive indices and dispersion, elemental analyses, and fluorescence, as well as infrared, visible, or infrared absorption frequencies, etc. One or more of these microscopes are used in every area of the physical sciences—biology, chemistry, and physics; and also in their subsciences: mineralogy, histology, cytology, pathology, metallography, etc.
Genetic Engineering, Microbes
Authors: Nagarajan Vasantha
Published: August 2004

The techniques involved in isolation and manipulation of genes from several microbes have become routine. Genes are cloned into plasmid or phage‐based vectors and introduced into the microbe of choice. The number of vectors that have been engineered to be versatile is on the increase for several systems. Some vectors are commercially available for gene manipulations from several vendors. In addition, construction of gene libraries and screening are also performed by small biotechnology companies. Most of the reagents needed for gene manipulation such as oligonucleotides, peptides, and antibodies are commercially available. In addition, kits are also accessible for some of the routine tasks such as plasmid isolation, deoxyribonucleic acid (DNA) sequencing, etc. The methods involved in the production of proteins in microbes are those of gene expression. Genetically engineered microbes are used to produce several commercial products. The number of products is likely to increase. They include therapeutics, bulk enzymes, antibiotics, chemicals, and crop protection products.
Molybdenum and Molybdenum Alloys
Authors: Doane D. V. , Timmons G. A. , Hallada C. J.
Published: August 2004

Molybdenum, a key industrial element, is used both in its pure form as a refractory metal and as an alloying element in irons and steels. Most molybdenum production is in North America, although some metal comes from other areas, especially from South America and China. The largest source of molybdenum is copper mines, where the former metal is a by‐product. Molybdenum supply, ore‐processing to commercial products, and the associated environmental considerations are reviewed.

Tools, pipelines, pumps, and various gears and dies, especially those for harsh working environments such as those found in the petroleum industry, are made from molybdenum containing alloys. The molybdenum imparts strength, hardness, and corrosion resistance to steels and cast irons. Molybdenum is a refractory metal used in furnaces, electrodes, light bulbs, and x‐ray tubes. Properties and uses are described.
Graphite, Natural
Authors: Taylor Harold A.
Published: August 2004

Natural graphite, the mineral form of graphitic carbon, occurs worldwide. It differs from the carbon of coal and of diamond in its predominantly lamellar hexagonal crystal structure. The ore usually contains associated silicate minerals that vary in kind and amount with the source. The name natural graphite is used in technical terminology and sometimes elsewhere. It may be simply termed graphite or any of several common names such as plumbago, black lead, silver lead, carburet of iron, and reissblei. The macrophysical form depends on geological genesis, whereas the properties depend on both the macrophysical form and associated mineral suite. The commercial value depends on specific characteristics such as form, percentage and kind of mineral suite, and availability. Graphite occurs in widely distributed places as flakes, lumps, and cryptocrystalline masses referred to commercially as amorphous graphite. Parallel layers of condensed planar C6‐rings constitute the graphite crystallite. Weak van der Waals forces pin the carbons in adjoining layers, thus accounting in part for the marked anisotropic properties of the graphite crystal. Solid articles made of natural graphite always require a binder; ie, they are always composites. Graphite's strength increases as the temperature rises. Graphite burns slowly in air above 450°C, the rate increasing with temperature and exposed area. Graphite can be regenerated from the crystal compounds because the graphitic structure has not been too greatly altered. The dark crystal compounds are called intercalation compounds, interstitial compound, or lamellar compounds because they are formed by reactants that fit in between the planar carbon networks. The covalent compounds of graphite differ markedly from the crystal compounds. They are white or lightly colored electrical insulators and have ill‐defined formulas. In the covalent compounds, the carbon network is deformed, and the carbon atoms rearrange tetrahedrally as in diamond. Often they are formed with explosive violence. The many useful properties of graphite give rise to a wide variety of products: unctuous, dry lubricant; marks readily, writing and drafting pencils; combination of lubricity and electrical conductivity, motor and generator brushes; and burns slowly, conducts heat, and retains strength over a large temperature range, refractories such as crucibles, carbon–magnesite brick, and continuously casting ware.
Peptides
Authors: Wise Edmund M.
Published: August 2004

Peptide antibiotics are classified according to their overall shape, which can be linear or cyclic, and by the nature of the bonds joining the constituent amino acids and other carboxylic acids, which can be all amide bonds or amide plus ester bonds. Most peptide antibiotics are cyclic peptides that do not contain disulfide linkages. Peptide antibiotics differ in many respects from proteins. The vast majority of peptide antibiotics have molecular weights in the 500–1500 range, whereas the average protein has a mol wt of 40,000. Many peptide antibiotics have unusual fatty acids and amino acids, such asD‐amino acids,N‐methyl amino acids, or imino acids, and they usually lack methionine and histidine. Ring closure in cyclic peptide antibiotics is by amide or ester bonds. Peptide antibiotics are normally resistant to the usual proteases and peptidases. They are usually synthesized on multienzyme complexes much as are fatty acids, and not on ribosomes as are proteins. Most peptide antibiotics are synthesized as groups of closely related structures. Even the small fraction of peptide antibiotics that have therapeutic usefulness are quite toxic. The ratio of the minimum toxic dose to the maximum effective dose is smaller than for most nonpeptide antibiotics. Peptide antibiotics are not often the drugs of first choice for systemic therapy of important human disease. However, the World Health Organization, which chooses drugs especially for Third World use based on efficacy, safety, quality, price, and availability, includes such peptide antibiotics as bleomycin, dactinomycin, and bacitracin, plus several β‐lactams. The complex structure of peptide antibiotics adds considerably to the problems of synthesis, but more recent efforts toward improved peptide antibiotics are encouraging.
Phenolic Resins
Authors: Kopf Peter W.
Published: August 2004

Phenolic resins are a family of polymers and oligomers composed of a wide range of structures based on the various reaction products of phenols with formaldehyde. Applications vary from commodity construction materials to high technology applications in electronics and aerospace. Phenolic resins are prepared using acidic or basic catalysts. Weak Lewis acids, such as zinc acetate, are used for specialty resins.

Phenolic novolaks are thermoplastic resins prepared from acid catalysts and a molar excess of phenol. They have a molecular weight of 500–5000 and a glass‐transition temperature,Tg, of 45–70°C. Novolak resins are typically cured with 5–15% hexamethylenetetramine as the cross‐linking agent. Resole‐type phenolic resins are produced with a molar ratio of formaldehyde to phenol of 1.2:1 to 3.0:1 and alkaline catalysts such as NaOH, Ca(OH)2, and Ba(OH)2. A typical resin has an initial molecular weight of 150 to perhaps 1500. For systems of unsubstituted phenols, the final cross‐link density is 150–300 atomic mass units per cross‐link.

In 1993, worldwide consumption of phenolic resins exceeded\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${3\times 10^{6}{\hskip0.167em}{\hskip0.167em}{\rm{t}}}$\end{document}; slightly less than half of the total volume was produced in the United States, where the largest‐volume application is in plywood adhesives and accounts for ca 49% of U.S. consumption. As a mature industry, U.S. production of phenolic resins has paralleled the growth in the GNP. Applications for phenolic resins include coatings, adhesives, carbonless copy paper, molding compounds, bonded and coated abrasives, friction materials, foundry resins, laminates, air and oil filters, wood bonding, fiber bonding, composites, spherical fillers, and fibers.

Factors contributing to the health and safety of phenolic resin are related primarily to the presence of unreacted phenol and formaldehyde. Unreacted phenol in a resin can range from\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${>{\hskip-0.167em}{\hskip-0.167em}10{\%}}$\end{document}for liquid resoles used in impregnation processes to\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${<{\hskip-0.167em}{\hskip-0.167em}1{\%}}$\end{document}for novolaks intended for use as epoxy hardeners. Free formaldehyde can be 2–4% in liquid adhesives.