bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption, Gas Separation
Authors: Yon Carmen M. , Sherman John D.
Published: July 2004

Gas‐phase adsorption is widely employed for the large‐scale purification or bulk separation of air, natural gas, chemicals, and petrochemicals. An adsorbent attracts molecules from the gas, and the molecules become concentrated on the surface of the adsorbent and are removed from the gas phase. Most commercial adsorbents for gas‐phase applications are employed in the form of pellets, beads, or other granular shapes, most commonly packed into fixed beds through which the gaseous feed mixtures are passed. The growth in both variety and scale of gas‐phase adsorption separation processes, particularly since 1970, is due in part to continuing discoveries of new porous, high surface‐area adsorbent materials (particularly molecular sieve zeolites) and to improvements in the design and modification of adsorbents. To permit the recovery of pure products and to extend the adsorbent's useful life, adsorbents should generally be inert and not react with or catalyze reactions of adsorbate molecules. Commercially useful adsorbents can be classified by the nature of their structure (amorphous or crystalline), by the sizes of their pores, by the nature of their surfaces (polar, nonpolar, or intermediate), or by their chemical composition, of which the size of the pores is the most important initial consideration. Adsorption processes are temperature‐swing adsorption (TSA) and pressure‐swing (PSA) as well as purge‐swing cycles and nonregenerative approaches. Most adsorption processes use fixed beds, but some use moving‐ or fluidized‐beds or wheels.
Aerosols
Authors: Sciarra John J. , Sciarra Christopher J.
Published: July 2004

The aerosol container has enjoyed commercial success in a wide variety of product categories. Insecticide aerosols were introduced in the late 1940s, and shave foams, hair sprays, deodorants, paints, perfumes, whipped cream, and automotive products followed in the 1950s. Medicinal metered‐dose aerosol products have also been developed for use in the treatment of asthma, migraine headaches, and angina. Aerosol products are hermetically sealed, ensuring that the contents cannot leak, spill, or be contaminated. The packages can be considered to be tamper‐proof. They deliver the product in an efficient manner, generating little waste, often to sites of difficult access. By control of particle size, spray pattern, and volume delivered per second, the product can be applied directly without contact by the user. All aerosols consist of product concentrate, propellant, container, and valve (including an actuator and dip tube). The propellant, said to be the heart of an aerosol system, maintains a suitable pressure within the container and expels the product once the valve is opened. Propellants may be either a liquefied halocarbon, hydrocarbon, or halocarbon–hydrocarbon blend, or a compressed gas such as carbon dioxide, nitrogen, or nitrous oxide. Worldwide, use of CFC propellants, designated as Propellants 11, 12, and 114, is strictly limited to specialized medicinal aerosol products such as metered‐dose inhalers. The most popular aerosol containers are the three‐piece, tin‐plated steel container and the aluminum container. All aerosols are produced by either a cold‐filling or pressure‐filling process. Barrier packs utilize a plastic bag or piston to separate the product from the propellant.
Alcohols, Polyhydric
Authors: Hunter William N.
Published: July 2004

Polyhydric alcohols or polyols contain three or more CH2OH functional groups. The monomeric compounds have the general formula R(CH2OH)n, whereand R is an alkyl group or C.CH2OH; the dimers and trimers are also commercially significant. Each polyhydric alcohol is a white solid, ranging from the crystalline pentaerythritols to the waxy trimethylol alkyls. The trihydric alcohols are very soluble in water, as is ditrimethylolpropane. Pentaerythritol is moderately soluble and dipentaerythritol and tripentaerythritol are less soluble. Pentaerythritol and trimethylolpropane have no known toxic or irritating effects. Finely powdered pentaerythritol, however, may form explosive dust clouds. Pentaerythritol is produced by reaction of formaldehyde and acetaldehyde in the presence of a basic catalyst, generally an alkali or alkaline‐earth hydroxide. Dipentaerythritol and tripentaerythritol are obtained as by‐products of the pentaerythritol process and may be further purified by fractional crystallization or extraction. Pentaerythritol and trimethylolpropane are classified as nuisance particulate and dust, respectively. The most important industrial use of pentaerythritol is in a wide variety of paints, coatings, and varnishes, where the cross‐linking capability of the four hydroxy groups is critical.
Alcohol Fuels
Authors: Jackson Michael D. , Moyer Carl B.
Published: July 2004

A wide variety of countries have, at various times, explored the use of either methanol or ethanol alcohol fuels as alternatives to diesel and gasoline fuels. Recently the United States has demonstrated light and heavy‐duty vehicles using alcohols but has not yet passed beyond the use of limited amounts of alcohols as gasoline components. The potential benefits of alcohol fuels include increased energy diversification accompanied by some energy security and balance of payments benefits, and air quality improvements. The Clean Air Act of 1990, emission standards set out by the State of California, and the 1992 Comprehensive National Energy Policy Act may serve to encourage the substantial use of alcohol fuels, unless gasoline and diesel technologies offer comparable advantages. Both methanol and ethanol have high octane values and allow high compression ratios providing increased efficiency and improved power output per cylinder. The properties of methanol and ethanol result in different vehicle fuel storage considerations. Unlike gasoline or diesel fuel, the vapor of methanol or ethanol above the liquid fuel in a fuel tank is usually combustible at ambient temperatures. This poses the risk of an explosion should a spark or flame find its way to the tank such as during refueling. The 85% methanol–15% gasoline fuel in use in California and elsewhere is commonly called M85. If methanol is to compete with conventional gasoline and diesel fuel it must be readily available and inexpensively produced. Thus methanol production from a low‐cost feedstock such as natural gas or coal is essential. Ethanol is primarily produced from a variety of crops and crop by‐products, generically called renewable biomass. In general, the low cost estimates for alcohol fuels indicate that methanol produced on a large scale from low cost natural gas could compete with gasoline when oil prices are around 14¢/L ($27/bbl). The future market response to new forms of emissions regulation is unknown. It is possible that the new emissions standards will simply result in improved gasoline technologies, and that the market result of the new standards will simply be cleaner gasolines. However, in 1990 the U.S. Alternative Fuels Council agreed on a goal of a 25% share of nonpetroleum transportation fuels by 2005. Alcohol fuels could capture a large part of this 25% share of nonpetroleum fuels.
Aldehydes
Authors: Abatjoglou Anthony G. , Miller David J.
Published: July 2004

Aldehydes are carbonyl‐containing organic compounds of the general formula RCHO. The group R represents an aliphatic, aromatic, heterosubstituted radical, except in formaldehyde, where R represents hydrogen. Aldehydes are inherently reactive compounds. The carbonyl group is susceptible to both oxidation and reduction, yielding acids and alcohols, respectively. The common method of naming aldehydes corresponds very closely to that of the related acids in that the termaldehydeis added to the base name of the acid. The C1and C2carbon aliphatic aldehydes, formaldehyde and acetaldehyde, are gases at ambient conditions whereas the C3(propanal) through C11(undecanal) aldehydes are liquids, and higher aldehydes are solids at room temperature. The lower, C1to C8aldehydes have pungent, penetrating, unpleasant odors. Above C8, aldehydes have more pleasant odors and some higher aldehydes are used in the perfume and flavoring industries. Reactions of aldehydes generally fall into two classes: those directly affecting the carbonyl group and those involving the adjacent carbon atom. There are, acute effects of aldehydes: eye, skin, and respiratory tract irritation, as well as organ pathology. Aldehydes find the most widespread use as chemical intermediates. A large proportion of aldehydes are converted to alcohols for use as solvents and in the manufacture of plasticizers. Fatty aldehydes C8to C13are used in nearly all perfume types and aromas.
Alkanolamines from Nitro Alcohols
Authors: Eachus Alan C. , Bollmeier Allen F.
Published: July 2004

The nitro alcohols obtained by the condensation of nitroparaffins with formaldehyde may be reduced to a unique series of alkanolamines (β‐amino alcohols). The five primary amino alcohols manufactured on a commercially significant scale are 2‐amino‐2‐methyl‐1‐propanol (AMP), 2‐amino‐2‐ethyl‐1,3‐propanediol (AEPD), 2‐amino‐2‐(hydroxymethyl)‐1,3‐propanediol (TRIS AMINO), 2‐amino‐2‐methyl‐1,3‐propanediol (AMPD), and 2‐amino‐1‐butanol (AB). 2‐dimethylamino‐2‐methyl‐1‐propanol (DMAMP) is the only N‐substituted derivative of these compounds available in commercial quantities. These six commercial alkanolamines are highly soluble in water. They are generally very soluble in alcohols, slightly soluble in aromatic hydrocarbons, and nearly insoluble in aliphatic hydrocarbons. According to current U.S. Department of Transportation regulations, AMP, AMP‐95, DMAMP, DMAMP‐80, AEPD, and AB are all classified as combustible liquids. The commercial alkanolamines exhibit the chemical reactivity of both amines and alcohols, as do other alkanolamines. Typically, they will attack copper, brass, and aluminum, but not steel or iron. Alkanolamines are useful as amination agents. The reduction of nitro alcohols to alkanolamines is accomplished by hydrogenation in the presence of Raney nickel catalyst. Alkanolamines are only slightly toxic by ingestion. Undiluted DMAMP, AMP‐95, and AB cause eye burns and permanent damage if not washed out immediately. The 40% aqueous solution of TRIS AMINO is nonirritating to the eyes and skin. Alkanolamines are used in emulsions, pigment dispersion, resin solubilizers, catalysts, applications in oil and gas production, and in biomedical and synthetic applications.
Alkyd Resins
Authors: Wicks Zeno W.
Published: July 2004

Chemistry, processing, and uses of various types of alkyds are discussed including oxidizing and nonoxidizing alkyds, high solids, styrenated alkyds, siliconized alkyds, and waterborne alkyd resins. Also covered are the related uralkyd and epoxy ester resins.
Allyl Monomers and Polymers
Authors: Dowbenko R.
Published: July 2004

Allyl compounds comprise a large group of ethylenic compounds having unique reactivities and uses often contrasting with those of typical vinyl‐type compounds. Unlike monovinyl compounds, monoallyl compounds do not form homopolymers of high molecular weight by free‐radical or conventional ionic mechanisms. In contrast, many allyl compounds containing two or more reactive double bonds yield solid, high molecular weight polymers by initiation with suitable free‐radical catalysts. A number of polyfunctional allyl esters have achieved importance in polymerization and copolymerization, especially to obtain heat‐resistant cast sheets and thermoset moldings. Diallyl diglycol carbonate or diethylene glycol bis(allyl carbonate) (DADC) was developed to produce by bulk polymerization cast sheets, lenses, and other shapes of outstanding scratch resistance and optical and mechanical properties. Reaction of allyl alcohol in the presence of alkali with diethylene glycol bis(chloroformate) gives the DADC monomer, a colorless liquid of mild odor. The latter is low in toxicity, but can produce skin irritation. DADC is soluble in common organic solvents and in methyl methacrylate, styrene, and vinyl acetate. It is partially soluble in amyl alcohol, gasoline, and ligroin. It is insoluble in ethylene glycol, glycerol, and water. Usage of DADC polymers in impact‐resistant, lightweight eyewear lenses has grown rapidly and is now the principal application. The three isomeric diallyl phthalates are colorless liquids of mild odor, low volatility, and relatively slow polymerization in the early stages. At ca 25% conversion, the viscous liquid undergoes gelation and polymerization accelerates. Diallyl isophthalate (DAIP) polymerizes faster than DAP. Besides application as heat‐resistant molding powders for electronic and other applications, DAIP copolymers have been proposed for optical applications. The largest use of diallyl phthalate thermoset polymers is in moldings and coatings for electronic devices requiring high reliability under long‐term adverse environmental conditions. Monomers such as allyl methacrylate (AMA) and diallyl maleate (DAM) have applications as cross‐linking and branching agents selected especially for the different reactivities of their double bonds. DAM and DAF have pungent odors and are skin irritants. Allyl methacrylate (AMA) is used as cross‐linking agent with methacrylate esters in contact lenses. Triallyl cyanurate (TAC), 2,4,6‐tris(allyloxy)‐s‐triazine, and its isomer triallyl isocyanurate (TAIC) are used as cross‐linking agents with comonomers and for aftercuring preformed polymers such as olefin copolymers in electrical insulations.N,N‐Diallyldimethyl(DADM)ammonium salts are used for the preparation of polyelectrolytes. Copolymers of diallyldimethylammonium chloride with acrylamide have been used in electroconductive coatings.
Fluorine Compounds, Inorganic, Aluminum
Authors: Conley B. , Shaikh T. , Atwood D. A.
Published: July 2004

Both the binary and complex fluorides of aluminum have played a significant role in the aluminum industry. Aluminum trifluoride trihydrate is of primary importance to the manufacture of aluminum as is sodium hexafluoroaluminate, known as cryolite. Anhydrous aluminum fluoride is used in fluoride glass manufacture and in ceramics. Mixtures of potassium tetrafluoroaluminate and potassium hexafluoroaluminate have been employed as brazing fluxes in the manufacture of aluminum parts. Two new types of aluminates with far ranging commercial potential have been prepared and characterized. The properties, manufacture, and uses of the various aluminum fluoride compounds are described.
Aminoglycosides
Authors: McGregor Donald
Published: July 2004

Aminoglycosidesare members of the class of antibacterial antibiotics, the structures of which are derived fromD‐streptamine,D‐2‐deoxystreptamine, or closely related compounds. The termaminocyclitolis sometimes used to identify this group of compounds. In 1991, the most widely used aminoglycosides in medical practice were gentamicin, tobramycin, amikacin, and netilmicin. In general, the aminoglycosides are useful for the treatment of serious infections involving aerobic or facultative gram‐negative bacilli. The most common resistance mechanism involves the inactivation of the aminoglycoside by reactions catalyzed by plasmid‐borne enzymes. Less common resistance mechanisms include decreased affinity for the antibiotic by the bacterial ribosome and decreased rate of transport into the bacterial cytoplasm. The aminoglycosides are administered primarily by intravenous infusion or intramuscular injection. Most of the administered dose is eliminated unmetabolized in the urine. Potential toxicity is a primary limiting factor in the clinical use of aminoglycosides. The most important toxicities are nephrotoxicity, ototoxicity, and to a lesser extent, neuromuscular blockade. All the aminoglycosides in medical practice are capable of causing these adverse events. The effect of this potential is to prevent the use of significantly increased doses to cover difficult infections. The bactericidal mechanisms employed by aminoglycosides are incompletely understood. In the cytoplasm, ribosomal binding leads to misreading of the genetic code and production of abnormal proteins and protein synthesis inhibition. The cause of cell death is uncertain. A large amount of research has been conducted aimed at reducing the limitations in the areas of toxicity and susceptibility to bacterial resistance mechanisms while maintaining the advantages by modification of the aminoglycoside molecular structure. Overall, structural modification has been successful in reducing susceptibility to bacterial inactivation. It has not been possible, however, to substantially dissociate the toxicity potential from the antibacterial activity.
Amines by Reduction
Authors: Schilling Steven L.
Published: July 2004

Amines are derivatives of ammonia in which one or more of the hydrogens is replaced with an alkyl, aryl, cycloalkyl or heterocyclic group. When more than one hydrogen has been replaced, the substituents can either be the same or different. Amines are classified as primary, secondary, or tertiary depending on the number of hydrogens which have been replaced. Many different types of nitrogen‐containing compounds can be reduced to amines. In practice, however, nitriles or nitro compounds are usually used because they are the most easily obtained starting materials. There are several commercial processes for reducing nitro or nitrile groups to amines. Most large volume aromatic and aliphatic amines are made by continuous high‐pressure catalytic hydrogenation. Nitro compounds can also be reduced in good yields with iron and hydrochloric acid in the Bèchamp process. Aromatic amines are usually made by hydrogenating the corresponding nitro compound, whereas the aliphatic amines generally start with the corresponding nitrile. In the Bèchamp process, nitro compounds are reduced to amines in the presence of iron and an acid. This is the oldest commercial process for preparing amines, and is still used in the dyestuff industry. The method of reducing aromatic nitro compounds with divalent sulfur is known as Zinin reduction. This reaction is carried out in a basic media using sulfides, polysulfides, or hydrosulfides as the reducing agent. Amines, nitro compounds, nitriles, and the various solvents and reagents used in the preparation of amines by reduction vary widely in the hazards they may pose. Some of these materials are acutely toxic by ingestion, inhalation, or absorption through the skin. Others are skin irritants or sensitizers. Still others, by chronic exposure, may cause damage to organs such as the liver or may be carcinogenic. No general rules can govern their safe use in all cases. Regulations governing the safe handling and shipping of amines are given in U.S. Department of Transportation publications. Specific information on safe handling and hazards can be found in the Material Safety Data Sheet for a given material.
Amino Resins and Plastics
Authors: Williams Laurence L.
Published: July 2004

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

Ammonia is a colorless gas, is lighter than air and has a unique penetrating odor. It occurs naturally throughout the universe. This article lists the import properties of ammonia and discusses its manufacture. Ammonia is produced mainly by the steam reforming of methane. This process is discussed in detail. Information on other production processes is given. Ammonia is a world‐class commodity. U.S. and global capacity data are presented along with a listing of U.S. producers. Ammonia produced by steam reforming is relatively clean, but ammonia produced from heavy feedstocks can cause environmental problems. Ammonia is a strong local irritant. The largest use for ammonia is in the production of fertilizers. It is also used to produce chemicals such as caprolactam, acrylonitrile and hydrogen cyanide.
Semiconductors, Amorphous Semiconductors
Authors: Madan Arun
Published: July 2004

Amorphous hydrogenated silicon (a‐Si:H)‐based semiconductors dominate many application areas such as flat‐panel liquid crystal displays, high electrophotography, and photovoltaics. The uniqueness of amorphous silicon from a basic physics point of view is discussed with respect to its crystalline counterpart. The growth mechanism ofa‐Si:H using the plasma‐enhanced chemical vapor deposition (PECVD) technique and the interrelationship between some deposition parameters and the resulting optoelectronic properties of the film are outlined. This discussion is expanded to the use of these materials in various important applications and the primary companies involved in their manufacture.
Amyl Alcohols
Authors: Papa Anthony J.
Published: July 2004

Amyl alcohol describes any saturated aliphatic alcohol containing five carbon atoms. This class consists of three pentanols, four substituted butanols, and a disubstituted propanol, ie, eight structural isomers C5H12O: four primary, three secondary, and one tertiary alcohol. In addition, 2‐pentanol, 2‐methyl‐1‐butanol, and 3‐methyl‐2‐butanol have chiral centers and hence two enantiomeric forms. The odd‐carbon structure and the extent of branching provide amyl alcohols with unique physical and solubility properties and often offer ideal properties for solvent, surfactant, extraction, gasoline additive, and fragrance applications. Today the most important industrial process for amyl alcohol production is low pressure rhodium‐catalyzed hydroformylation (oxo process) of butenes. Mixtures of isomeric amyl alcohols (1‐pentanol and 2‐methyl‐1‐butanol) are often preferred because they are less expensive to produce commercially and have a more desirable combination of properties. With the exception of neopentyl alcohol (mp 53°C), the amyl alcohols are clear, colorless liquids under atmospheric conditions, with characteristic, slightly pungent and penetrating odors. Commercial primary amyl alcohol is a mixture of 1‐pentanol and 2‐methyl‐1‐butanol. Like the lower alcohols, amyl alcohols are completely miscible with numerous organic solvents and are excellent solvents for nitrocellulose, resin lacquers, higher esters, and various natural and synthetic gums and resins. However, in contrast to the lower alcohols, they are only slightly soluble in water. Important amyl alcohol reactions include dehydration, esterification, oxidation, amination, etherification, and condensation. Three significant commercial processes for the production of amyl alcohols include separation from fusel oils, chlorination of C‐5 alkanes with subsequent hydrolysis to produce a mixture of seven of the eight isomers (Pennsalt), and a low pressure oxo process. The oxo process is the principal one in practice today. The main effects of prolonged exposure to amyl alcohols are irritation to mucous membranes and upper respiratory tract, significant depression of the central nervous system, and narcotic effects from vapor inhalation or oral absorption. All the alcohols are harmful if inhaled or swallowed. 3‐Methyl‐1‐butanol has demonstrated carcinogenic activity in animal studies. The amyl alcohols are readily flammable substances;tert‐amyl alcohol is the most flammable. Their vapors can form explosive mixtures with air. Amyl alcohols are best stored or shipped in either aluminum, lined steel, or stainless steel tanks.
Hormones, Anterior Pituitary Hormones
Authors: Matteri Robert L.
Published: July 2004

The hormones of the anterior pituitary gland play a significant role in the maintenance of normal health and body function. This master gland produces hormones involved in the regulation of somatic growth, metabolic rate, carbohydrate and lipid metabolism, lactation, reproduction, and response to stress. Eleven anterior pituitary hormones have been extensively characterized at the protein and genomic levels. These hormones fall into three classic categories, ie, pro‐opiomelanocortin‐related (POMC‐related) hormones, proteins structurally related to prolactin and growth hormone (PRL/GH‐related), and glycoproteins. Structural similarities exist within each biochemical category, and the structural data presented represent listings in the Protein Identification Resource (PIR) database, compiled by the National Biomedical Research Foundation. Summary information on the principal biologic roles of each of these hormones is provided, as are commercial availability and source.
Antiaging Agents
Authors: Cottam Howard B.
Published: July 2004

The aging process in humans is extremely complex with many factors undoubtedly involved to some degree including environmental, dietary, and genetic influences. The process can be described as a physical decline and involves the buildup of cellular and molecular damage that increases our susceptibility to disease and infirmity as we grow older.

The current view of scientists is that random damage that occurs within cells and among extracellular molecules is responsible for many of the age‐related changes that are observed in organisms. Molecular disorder occurs and accumulates within cells and their products because this occurrence outpaces the cell's repair mechanisms. This article summarizes recent literature reports of research efforts directed toward intervention in the aging process as well as changes and diseases associated with the aging process involving all the major organ systems in humans. Consideration is given to pharmacological treatment and prevention of such age‐related changes and conditions.
Antimony and Antimony Alloys
Authors: Li T.
Published: July 2004

Antimony, Sb, belongs to Group 15 (VA) of the Periodic Table, which also includes arsenic and bismuth. World reserves of antimony are estimated to be ∼ 2.1 million metric tons. Most of the world's supply can be found in China, Bolivia, Russia, and the Republic of South Africa. Antimony is a slivery white, brittle solid. It is ordinarily quite stable and not readily attacked by air. Antimony is often associated with lead ores. The antimony content of commercial ores ranges from 5 to 60% and determines the method of treatment, either pyrometallurgical or hydrometallurgical. Process metallurgy details are given, as well as alternative methods of production. Antimony is available as cast cakes, ingots, broken pieces, granules, shot, and single crystals. The United States is not self‐sufficient in its requirements for antimony and much of it is imported. China supplies most of the needed antimony.

Uses for antimony include as compounds in flame retardants, transportation, (including batteries), chemicals, and glass.

Antimony is a common air pollutant and is released into the environment by burning fossil fuels and from industry. Antimony can enter the human body by ingestion of meats, vegetables, and seafood. Metallic antimony can be handled without danger, but it is recommended that direct skin contact be avoided. The bulk of secondary antimony has been recovered as antimonial lead.
Antiviral Agents
Authors: Hosmane Ramachandra S.
Published: July 2004

Since the discovery of the first virus >100 years ago, thousands of different viruses have been identified and characterized, and a number of plant, animal, and human ailments have been traced to viral origin. The rapid advances made in tools and techniques of molecular biology in the last 40 years, coupled with cooperative efforts in genetics and biochemical fronts, have afforded intricate details of the structure, function, replication, and genomic makeup of a host of viruses. As there are too many viruses to give even short accounts, this article focuses on only those that have some relevance to human diseases. But, since the list of all human viruses would still be too long to give detailed descriptions for each, the focus is further narrowed down to four major viruses that are currently perceived to threaten global health. These four viruses include HIV (human immunodeficiency virus, which causes AIDS), HBV and HCV (hepatitis B and C viruses that cause liver damage), and the more recent WNV (West Nile virus that causes brain inflammation). Nevertheless, an attempt has been made to classify all the known major viruses based on their shape, size, symmetry, hosts, and chemical composition that includes nucleic acid, protein, and presence or absence of lipid envelope.

As they are a form of life that cannot replicate outside a host cell, viruses have evolved to develop complex and diverse interactions with higher organisms. Therefore, it was long believed that the development of antiviral agents that would specifically disrupt the viral replication process without affecting the normal metabolic events of the host would be difficult. Thanks to excellent advances in virology, several targets that are unique to the viruses have now been identified and successfully explored. This article briefly describes the general processes of viral infection to point out potential targets for selective antiviral agents. These targets are then classified into two major virus‐specific processes, including (a) early events of viral adsorption, penetration and uncoating, and (b) later synthetic events that concern intracellular replication of the virus. While there are only limited choices of candidates dealing with the early events, a much larger pool of candidates exists for targeting the later events in a virus life cycle, and they are known to be virus‐specific. The viruses synthesize and utilize specific enzymes and proteins, and more importantly, the replication of viral genomes is also virus‐specific. Nucleoside analogues which target these later events of viral life cycles have played major roles as antiviral agents against almost all the major viruses, and therefore, a special emphasis has been placed on this class of compounds in this review article. Prophylactic measures such as vaccine immunization have also been discussed under each of the four major viruses mentioned.
Antiobesity Drugs
Authors: Tilley Jefferson W.
Published: July 2004

Obesity is a major medical problem in the United States. In the 1990s, an estimated 55% of the adult U.S. population were above their ideal body weights and as a consequence, were at risk for the development of various chronic ailments including diabetes, cardiovascular disease, and cancer. Both genetic and social factors contribute to the development of obesity. Currently available treatments include diet, exercise, anorectic sympathomimetic agents, and fat absorption inhibitors. Even though most patients are able to lose at least a portion of their excess weight, long‐term weight loss is extremely difficult to achieve, and behavior modification is an absolute requirement for ultimate success. The appetite suppressant drugs with significant sales, phenylpropanolamine, phentermine, and sibutramine, are based on stimulation of the sympathetic nervous system and are indicated only for short‐term treatment of obesity because of their side effect profile and lack of robust efficacy. The first fat absorption inhibitor, the pancreatic lipase inhibitor orlistat, was recently introduced to the U.S. market for use as an adjunct to a reduced‐calorie diet. Although drug treatment is not likely to replace diet and behavior modification for the control of obesity, newer therapeutic agents based on recent discoveries concerning the central nervous system integration of satiety signals and the mechanism of energy utilization in fat and skeletal muscle promise to provide new tools for the management of obesity. Presently, drugs hold only a minute share of the multibillion dollar weight loss market, but promise to capture a larger percentage, as more selective and effective agents become available.
Flame Retardants, Antimony and Other Inorganic Agents
Authors: Touval Irving
Published: July 2004

Antimony, boron, aluminum, tin, zinc, and molybdenum are inorganic flame retardants or flame‐retardant synergists used to improve the flame retardancy obtained from incorporating halogens in plastics. Combinations of the synergists and the halogens are used at lower concentrations than the halogens alone, resulting in more flame‐resistant plastics that have better physical properties. Antimony oxide is the most effective flame‐retarder synergist; alumina trihydrate is the most widely used. Synergists used in combination often enhance one another. The mechanisms of inorganic synergist‐halogen flame‐retarder systems are discussed for both the condensed and flame phases. A series of typical formulations for various polymer materials is given.
Aquaculture
Authors: Stickney Rorbert
Published: July 2004

Aquaculture is the rearing of aquatic organisms under controlled or semicontrolled conditions. It involves plant and animal rearing with the objectives of providing human food, recreational fishing, enhancement of commercially valuable stocks, recovery of endangered species, and the production of bait and ornamental species. Aquaculture is conducted in ponds, raceways, cages, and net‐pens. It may also involve suspending molluscs from rafts or ropes, rearing them in baskets or trays, or placing them on the bottom in the natural environment. Technology levels range considerably with the highest level being found in conjunction with recirculating systems. Culturists attempt to control water quality, reproduction and diseases. They also employ feeds specifically designed for the animals being produced. Most species are maintained in captivity throughout the life cycle. Selective breeding is often used as a means of improving stocks of cultured organisms. Diseases can pose significant problems for aquaculturists. Avoidance of stress reduces disease incidence, but treatments, including drugs and vaccines are available for at least some aquatic animal diseases. The final task of the aquaculturist is to ensure that the product reaches the processor in the best possible condition. Careful handling during harvest helps ensure product quality.
Aroma Chemicals
Authors: Zviely Michael
Published: July 2004

Aroma chemicals are an important group of organic molecules used as ingredients in flavor and fragrance compositions. These chemicals consist of natural, nature‐identical and artificial molecules.

There are 3000 different molecules that find use in the production of flavor and fragrance compositions. Synthetic ingredients play a major part as components due to their convenient availability and the relatively lower costs compared to natural molecules from isolation of relatively limited natural sources.

This chapter is for those who intend to get a clear overview of all kinds of aroma chemicals including the chemical structure and a brief odor description.
Arsenic and Arsenic Alloys
Authors: Carapella S. C.
Published: July 2004

Arsenic, although often referred to as a metal, is classified chemically as a nonmetal or metalloid and belongs to Group 15 (VA) of the Periodic Table (as does antimony). The principal valences of arsenic are,, and. Only one stable isotope of arsenic having mass 75 (100% natural abundance) has been observed. Metallic arsenic is stable in dry air, but when exposed to humid air the surface oxidizes, giving a superficial golden bronze tarnish that turns black upon further exposure. The amorphous form is more stable to atmospheric oxidation. Upon heating in air, both forms sublime and the vapor oxidizes to arsenic trioxide, As2O3. Elemental arsenic combines with many metals to form arsenides. Arsenic is widely distributed about the earth and has a terrestrial abundance of approximately 5 g/t. The most important commercial source of arsenic, however, is as a by‐product from the treatment of copper, lead, cobalt, and gold ores. Arsenic metal is also offered in high (ranging from 99.99% to in excess of) purity form for semiconductor applications. The predominant use of arsenic in the United States is in the manufacture of chemicals. The principal use of arsenic in the United States is in the preparation of wood preservatives for the protection of lumber and other wood products. Arsenic trioxide is the basic commodity of commerce from which a number of important chemicals are manufactured. Trace quantities of arsenic are added to lead–antimony grid alloys used in lead acid batteries. Phosphorized deoxidized arsenical copper (alloy 142) is used for heat exchangers and condenser tubes. The toxicity of arsenic ranges from very low to extremely high depending on the chemical state. Metallic arsenic and arsenious sulfide, As2S3, have low toxicity. Arsine is extremely toxic. The toxicity of other organic and inorganic arsenic compounds varies. Arsenic is classified as a carcinogen by the International Agency for Research on Cancer (IARC). The handling of arsenic in the work‐place should be in compliance with the U.S. Occupational Safety and Health Administration (OSHA) regulations. Precautions should be taken to avoid accidental generation of arsine gas. Disposal of arsenical products should be in compliance with Federal and local government environmental regulations.
Fluorine Compounds, Inorganic, Arsenic
Authors: Lindahl Charles B. , Mahmood Tariq
Published: July 2004

Antimony and arsenic both form a trifluoride and a pentafluoride as well as a very stable hexafluoroantimonate and a hexafluoroarsenate ion, respectively. The chemistry of antimony fluoride compounds is well studied. Antimony trifluoride is used as a mild fluorinating agent for the production of fluorocarbons and for nonmetals and metals for the replacement of other halides. It is also used in the manufacture of fluoride glass. Antimony pentafluoride is a moderate fluorinating agent and a powerful oxidizer. It is used to saturate double bonds and in the production of intercalated compounds of graphite. It is also used to produce superacid systems. Anhydrous metal salts can be used as uv catalysts for the production of polymers.

Arsenic trifluoride is used as a fluorinating agent, in semiconductors, and in the synthesis of hexafluoroarsenates. Arsenic pentafluoride is used as a fluorinating agent, in ion implantation, and to produce conductive polymers. However, environmental and regulatory concerns have severely limited these applications.
Arsenic—Environmental Impact, Health Effects, and Treatment Methods
Authors: Thirunavukkarasu O. S. , Viraraghavan T.
Published: July 2004

Arsenic contamination of surface and subsurface waters is reported in many parts of the world and is considered as a global issue. The enforcement of stringent arsenic standard for drinking water, because of health problems associated with the ingestion of arsenic contaminated water, call for an effective treatment technology for arsenic removal. Since the toxicity of arsenic depends on its speciation, it is essential to determine the individual arsenic species present in drinking water. Further, a better understanding of the occurrence of arsenic, health effects, and available technologies would help in the evaluation of risk and selection of an appropriate cost‐effective technology. This article provides an overview of these aspects. Various treatment methods used to remove arsenic from drinking water are also discussed.
Barium
Authors: Boffito Claudio
Published: July 2004

Barium, Ba, is a member of Group 2 (IIA) of the Periodic Table, where it lies between strontium and radium. Along with calcium and strontium, barium is classed as an alkaline∼arth metal, and is the densest of the three. Barium metal does not occur free in nature; however, its compounds occur in small but widely distributed amounts in the earth's crust, especially in igneous rocks, sandstone, and shale. The principal barium minerals are barytes (barium sulfate) and witherite (barium carbonate), also known as heavy spar. The latter mineral can be readily decomposed via calcination to form barium oxide, BaO, the ore used commercially for the preparation of barium metal. Barium is prepared commercially by the thermal reduction of barium oxide with aluminum. Barium metal is highly reactive, a property that accounts for its principal uses as a getter for removing residual gases from vacuum systems on cathode ray tubes (eg, in CRT tubes) and as a deoxidizer for steel and other metals. Pure barium is a silvery‐white metal, although contamination with nitrogen produces a yellowish color. The metal is relatively soft and ductile and may be worked readily. It is fairly volatile (though less so than magnesium), and this property is used to advantage incommercial production. It is an extremely reactive metal, and its compounds possess large free energies of formation Barium metal and most barium compounds are highly poisonous Barium ions act as a muscle stimulant and can cause death through ventricular fibrillation of the heart. Barium also presents a hydrogen explosion hazard if allowed to come into contact with water or atmospheric moisture, and must always be kept dry and preferably sealed in the shipping containers.
Beer and Brewing
Authors: Lewis Michael J.
Published: July 2004

Beer is typically made from cereal grains. These, however, contain starch and so various strategies are necessary to convert starch to fermentable sugars. Most beer is brewed from specially chosen barley that is wetted, partially germinated, and dried to make malt. This modifies the raw barley to a form suitable for brewing. When malt is ground up and mixed with hot water, malt enzymes rapidly degrade starch to yield a spectrum of fermentable sugars and unfermentable dextrins. The grain extract (wort) is then boiled for an hour with hops, primarily to add bitterness but also to sterilize it. After cooling, a chosen yeast strain is added and fermentation ensues with production of mostly alcohol and carbon dioxide but also a host of flavor compounds each in low concentration. These, in concert with the flavor materials from malt and hops, define beer characteristics, and the brewer's particular choice of yeast, malt, and hops defines a beer brand. The green beer is aged or matured by secondary treatment, filtered and carbonated, and then packaged at high speed and without oxygen access for presentation to the consumer. Beer has some nutritional value and modest daily consumption reduces the risk of coronary heart disease.
Benzyl Chloride, Benzal Chloride, and Benzotrichloride
Authors: Seper Karl W.
Published: July 2004

When toluene reacts with chlorine under experimental conditions that promote free‐radical chlorination, a mixture of benzyl chloride, benzal chloride, and benzotrichloride is obtained. The product distribution is determined in large part by the chlorine:toluene ratio. Competing reactions result in chlorination of the aromatic ring, reducing the yield of side‐chain chlorination products.

Benzyl chloride undergoes reactions typical of a reactive alkyl halide. Hydrolysis gives benzyl alcohol, reaction with ammonia yields benzylamines, and benzyl esters form by reaction with salts of carboxylic acids. Reaction with other nucleophiles yield substitution products; alkoxides give benzyl ethers and cyanide give phenylacetonitrile.

Benzal chloride is hydrolyzed to benzaldehyde and benzotrichloride to benzoic acid. Benzotrifluoride is formed by the reaction of benzotrichloride with anhydrous hydrogen fluoride. Reaction conditions have been determined for aromatic ring chlorination and nitration of benzyl chloride, benzal chloride, and benzotrichloride.

More than two‐thirds of benzyl chloride produced is used to make the plasticizer benzyl butyl phthalate. Nearly all of the benzal chloride produced is consumed in the manufacture of benzaldehyde. Benzotrichloride is used in the manufacture of benzoyl chloride and in the synthesis of the herbicide intermediatep‐chlorobenzotrifluoride.