bluuebunny/crossref_metadata_2025 huggingface dataset:
Glass
Authors: Boyd David C. , Danielson Paul S. , Thompson David A. , Velez Mariano , Reis Signo T. , Brow Richard K.
Published: July 2004

Both organic and inorganic materials may form glasses if their structure is noncrystalline, ie, if they lack long‐range order. This includes some plastics, metals, and organic liquids. In principle, rapid cooling could prevent crystallization of any substance if the final temperature is sufficiently low to prevent structural rearrangement. Thus glasses are formed primarily for kinetic reasons.

Glasses can be prepared by methods other than cooling from a liquid state, including from solid/crystalline state and vapor phases by ultrafast grinding procedure.

Conditions favorable for glass formation may be deduced from either geometric or bond strength considerations. Glass formation of individual oxides can be predicted from the melting point, and individual bond energies can be normalized by dividing by the melting point of the oxide. Glass is a good medium for controlled crystallization, and has become the basis for a number of unique crystalline materials known as glass‐ceramics. Glass manufacture requires four major stages: batch preparation, meltings and refining, forming, and post‐forming.

Most glass articles are manufactured by a process in which raw materials are converted at high temperatures to a homogeneous melt that is then formed into the articles. Molten glass is either molded, drawn, rolled, or quenched, depending on desired shape and use.

Glass has lost to market share to aluminum and plastic for containers. Glass recycling, however, benefits the manufacturer and help shrink the high cost of waste disposal.

Glass is used in architecture, beverage containers, and insulation. Newer uses such as components in batteries, switches, glass‐ceramics, sol–gel glasses are discussed.
Glasses, Organic–;Inorganic Hybrids
Authors: Brennan A. B. , Miller T. M.
Published: July 2004

The search for new high performance materials has spurred the development of composites combining high modulus/high thermal stability inorganic glasses and low modulus/low thermal stability polymeric glasses. Research has resulted in a novel class of amorphous polymer–glass composites referred to as organic–inorganic hybrids or inorganic–organic hybrids, depending on the component with the highest volume fraction. These materials are synthesized in a variety of ways but ultimately exhibit near‐molecular‐level mixing of the matrix and the filler. Hence the term hybrid. Typically, this high degree of mixing results in transparent materials which exhibit significant increases in thermomechanical properties owing to extensive interaction between the polymeric and inorganic phases. However, the relatively high volume fraction of polymer included in these materials normally limits their service temperatures to well below 400°C. Many polymers and oligomers have been utilized in the synthesis of these hybrids, including poly(alkenes, acrylates, ethers, esters, amides, imides, and dienes). Some novel inorganic precursors have been used, such as clay. The use of metal alkoxides have been reported.

There are several areas of application for organic–inorganic hybrids: microelectronic usage, abrasion‐resistant coatings, thermal–oxidative‐resistant coatings, nonlinear optical devices, hydrogels, biosensors, and cross‐linking agents.
Glass‐Ceramics
Authors: Pinckney Linda R.
Published: July 2004

As materials formed by the controlled nucleation and crystallization of glass, glass‐ceramics can combine the advantages of glass with the optical and mechanical benefits of crystals. Commercial glass‐ceramics are used in applications requiring high thermal and mechanical stability, with products including radiant cooktop panels, telescope mirrors, cookware, and dental and medical prostheses. In addition to these products, future applications for glass‐ceramics are likely to capitalize on designed‐in, highly specialized properties for the transmission, display, and storage of information.
Recycling, Glass
Authors: Ross C. Pp
Published: July 2004

Ross, C. Philip (Creative Opportunities, Inc.). The properties of glass provide attributes for many commercial products. As some of these products reach the end of their useful life and are discarded, there is the opportunity to have the material recycled into other useful products. This alternative is preferred over having the material enter a municipal waste stream for landfill disposal. Glass can be remelted and refabricated over and over again without any deterioration of the material properties. Limitations for recycling of glass involve the level of contamination from other categories or colors of glass, as well as from a variety of nonglass materials. For successful recycling, glass must be processed in a manner consistent with the requirements of the glass manufacturing industry. Vol. 20, pp. 1127–1134, 10 refs. to April 1995.
Glycopeptides (Dalbaheptides)
Authors: Cavalleri B. , Parenti F.
Published: July 2004

The vancomycin–ristocetin family of glycopeptides is a subclass of linear sugar‐containing peptides composed of seven amino acids cross‐linked to generate a specific stereochemical configuration. This configuration forms the basis of a particular mechanism of action, eg, complexation with theD‐alanyl‐D‐alanine terminus of bacterial cell wall components. The term dalbaheptide, fromD‐al (anyl‐D‐alanine)b(inding)a(ntibiotics) having hept(apept)ide structure, has been proposed to distinguish them within the larger and diverse groups of glycopeptide antibiotics. About 40 different naturally produced dalbaheptides have been reported. Among them, vancomycin and teicoplanin are used clinically as a result of high activity against gram‐positive pathogens such as many coagulase‐negativeStaphylococci(CNS), corynebacteria,Clostridium difficile, multiresistantStaphylococcus aureus, and highly gentamicin‐resistantEnterococciwhich are refractory to established drugs. Eremomycin is under clinical evaluation. Many patents claim feed‐utilization efficiency increase and growth promotion in domestic animals for several dalbaheptides but only avoparcin (Avotan) is commercially used. Knowledge of the mechanism of action and investigations on the physicochemical characteristics has stimulated the transformation of natural antibiotics into new dalbaheptide derivatives using both chemical and biosynthetic modification. All the dalbaheptides are produced by strains belonging to the order ofActinomycetales. Dalbaheptides are produced by submerged fermentation. Pure dalbaheptides are obtained as colorless or whitish amorphous powders that usually retain water and solvents. Dalbaheptides are generally water‐soluble. Teicoplanin can be obtained as an internal salt or as a partial monoalkaline (sodium) salt. Other dalbaheptides are obtained as acidic salts. Dalbaheptides are levorotatory. The basis of the antibacterial action of dalbaheptides is the ability to form a complex with the terminalD‐Ala‐D‐Ala residues of growing peptidoglycan chains, thus preventing transglycosylation, eg, chain elongation, and transpeptidation, eg, cross‐linking. The consequent defective cell wall stops bacterial growth and eventually leads to cell death. Only three dalbaheptides are commercialized: vancomycin and teicoplanin for human health, and avoparcin for animal usage. Vancomycin and teicoplanin as formulated drugs are lyophilized powders to be reconstituted with sterile water for injection.
Glycerol
Authors: Morrison Lowen R.
Published: July 2004

Glycerol, a trihydric alcohol, is a clear, water‐white, viscous, sweet‐tasting hygroscopic liquid at ordinary room temperatures above its melting point. Glycerol occurs naturally in combined form as glycerides in all animal and vegetable fats and oils, and is recovered as a by‐product when these oils are saponified in the process of manufacturing soap, when the fats are split in the production of fatty acids, or when fats are esterified with methanol in the production of methyl esters. Since 1949 it has also been produced commercially by synthesis from propylene.

The uses of glycerol number in the thousands, with large amounts going into the manufacture of drugs, cosmetics, toothpastes, urethane foam, synthetic resins, and ester gums. Tobacco processing and foods also consume large amounts either as glycerol or glycerides.

Glycerol, is generally recognized as safe (GRAS) as a miscellaneous or general‐purpose food additive and it is permitted in certain food packaging materials. Glycerol derivatives include acetals, amines, esters, and ethers. Glyceryl trinitrate (nitroglycerin) is used in explosives and as a heart stimulant. Included among the esters also are the ester gums and, mono‐ and diglycerides used as emulsifiers and in shortenings. The salts of glycerophosphoric acid are used medicinally.
Gold and Gold Compounds
Authors: Cohn J.G. , Stern Eric W. , Etris Samuel F.
Published: July 2004

Gold is found as a relatively pure solid on the surface of the earth. It is widely distributed, but in very small concentrations. Gold is the most noble of the noble metals. Gold's properties are listed. The recovery of gold from ore is by the cyanidation process.

Specifications and requirements of the international trading markets are discussed as well as precautions aganist fraud. Gold is very recyclable because of its value. Gold is benign to the enviornment, but the chemicals used in its mining are not. Gold is used in electronics, jewelery, coins, decoration, dentistry and medicine.
Grignard Reactions
Authors: Silverman Gary S. , Rakita Philip E.
Published: July 2004

The termGrignard reactionrefers to both the preparation of a class of organomagnesium halide compounds and their subsequent reaction with a wide variety of organic and inorganic substrates.

The general sequence of the reactions is now embodied in the following generic forms, where RX = an organic halide (most typically a chloride or bromide, although fluorides can be induced to react); S = a coordinating solvent (such as an ether or an amine); and AZ = a substrate with an electronegative group, Z: RX + Mg +nS → RMgX·SnRMgX·Sn+ AZ → RAZMgX·SnRAZMgX·Sn→ RA + ZMgX·Sn.

The development of improved industrial procedures, including the substitution of tetrahydrofuran (THF) for diethyl ether and the demonstration that the less reactive, but significantly less expensive, vinyl and aryl chlorides could be successfully used, has greatly expanded the commercial possibilities of this reaction. In the flavor, fragrance, pharmaceutical, and fine chemical industries, its use can generally be regarded as routine.

The great value of the Grignard reaction to the synthetic chemist is its general applicability as a building block for an impressive range of structures and functional groups.

Preparation of Grignard Reagents

A Grignard reagent is prepared by first adding magnesium and a partial charge of solvent to the reactor, followed by the addition of RX, in the remaining solvent, to the reaction flask.

In spite of its industrial use for many years, the commercial‐scale production of Grignard reagents has not been extensively described.

The Grignard reaction has been commercially important for a number of years, and for certain industrial processes it remains the favored (or only) practical route to construct various element‐to‐carbon bonds.

There are five components to the cost of using a Grignard reagent:(1)magnesium metal,(2)the halide,(3)the solvent,(4)the substrate, and(5)disposal of the by‐products.

Reactions and applications of Grignard reagents include asymmetric syntheses using Grignard reagents, Grignard reactions with inorganic chlorides, Grignard reagents as bases, metal‐assisted modified Grignard reactions, intramolecular Grignard reactions, Grignards as methacrylate polymerization catalysts, and Grignard reagents as supports for the Ziegler‐Natta process.
Halogen Fluorides
Authors: Bailey Webb I. , Woytek Andrew J.
Published: July 2004

There are eight known halogen fluorides, binary compounds of fluorine with chlorine, bromine, and iodine. The halogen fluorides are highly reactive, powerful oxidizing agents that exist as noncryogenic liquids, offering a storable liquid source of fluorine at low pressure. Properties are described.

Chlorine trifluoride, bromine trifluoride, and iodine pentafluoride are available commercially. Chlorine trifluoride is used in the processing of nuclear fuels, bromine trifluoride as a chemical cutting agent for oil well pipe and tubing, and iodine pentafluoride as a fluorinating agent for organic compounds.
Acetic Acid, Halogenated Derivatives
Authors: Morris Earl D. , Bost John C.
Published: July 2004

The most important of the halogenated derivatives of acetic acid is chloroacetic acid, which has wide applications as an industrial chemical intermediate in the manufacture of cellulose ethers, herbicides, and thioglycolic acid. Most chloroacetic acid is produced by the chlorination of acetic acid. Chloroacetic acid is extremely corrosive and will cause serious chemical burns. It is readily absorbed through the skin; contamination of 5–10% of the skin is usually fatal. Sodium chloroacetate, C2H2ClO2Na, is produced by reaction of chloroacetic acid with sodium hydroxide or sodium carbonate. Dichloroacetic acid, C2H2Cl2O2, is a reactive intermediate in organic synthesis. It has been manufactured by the chlorination of acetic and chloroacetic acids and by other means. Trichloroacetic acid, C2HCl3O2, forms white deliquescent crystals. Sodium trichloroacetate, C2Cl3O2Na, is used as a herbicide. Chloroacetyl chloride (ClCH2COCl) is the corresponding acid chloride of chloroacetic acid, and is manufactured by reaction of chloroacetic acid with chlorinating agents. Much of the chloroacetyl chloride produced is used captively as a reactive intermediate. It is useful in many acylation reactions and in the production of adrenalin, diazepam, and chloroacetic anhydride. Two chloroacetate esters of industrial importance are methyl chloroacetate, C3H5ClO2, and ethyl chloroacetate, C4H7ClO2. Both are used as agricultural and pharmaceutical intermediates. Other derivatives are bromoacetic acid, dibromoacetic acid, tribromoacetic acid, iodoacetic acid, diiodoacetic acid, and triiodoacetic acid.
Flame Retardants, Halogenated
Authors: Pettigrew Alex
Published: July 2004

Halogenated, brominated, and chlorinated organic flame retardants are widely used to reduce the flammability or ignitability of plastics; this use is growing because of increasingly strict flammability regulations. Brominated and chlorinated aliphatic and brominated aromatic compounds are used as additives to both thermoset and thermoplastic polymers. Brominated aliphatic, brominated aromatic, and chlorinated aromatic compounds are used as reactive flame retardants in both thermoset and thermoplastic polymers. In many applications, antimony oxide is used as a synergist, interacting with halogenated flame retardants to produce a more effective system. The largest volume brominated flame retardants are the brominated aromatics tetrabromobisphenol A and decarbromodiphenyl oxide. The largest volume chlorinated flame retardants are the chlorinated paraffins. The toxicity of these materials is discussed.
Hazard Analysis and Risk Assessment
Authors: Crowl Daniel A.
Published: July 2004

The purpose of hazard analysis and risk assessment in the chemical process industry is to
(1)
characterize the hazards associated with a chemical facility;
(2)
determine how these hazards can result in an accident; and
(3)
determine the risk, ie, the probability and the consequence of these hazards. Methods for performing hazard analysis and risk assessment include safety review, checklists, Dow Fire and Explosion Index, what‐if analysis, hazard and operability analysis (HAZOP), failure modes and effects analysis (FMEA), fault tree analysis, and event tree analysis.

In order to complete an assessment of risk, a probability must be determined.

A more recent concept that could have significant impact on future designs is that of inherent safety. Hazard avoidance is performed by three techniques. First, there is substitution. This means substituting a less hazardous material for the material in use. The second method for inherent safety is attenuation, ie, operating the process at lower temperatures and pressures. The last inherent safety technique is intensification. This means using much smaller inventories of hazardous raw and intermediate materials, and reducing process hold‐up and inventories.
Heat‐Exchange Technology, Heat Pipes
Authors: Bienert Walter B. , Ernst Donald M. , Eastman G. Yale
Published: July 2004

Heat pipes are used to perform several important heat‐transfer roles in the chemical and closely allied industries. Examples include heat recovery, the isothermalizing of processes, and spot cooling in the molding of plastics. In its simplest form the heat pipe possesses the property of extremely high thermal conductance, often several hundred times that of metals. As a result, the heat pipe can produce nearly isothermal conditions making an almost ideal heat‐transfer element. In another form the heat pipe can provide positive, rapid, and precise control of temperature under conditions that vary with respect to time.

The heat pipe is self‐contained, has no mechanical moving parts, and requires no external power other than the heat that flows through it.
Heat‐Resistant Polymers
Authors: Cassidy Patrick E. , Aminabhavi Tejraj M. , Reddy V. Sreenivasulu
Published: July 2004

The intensive interest in heat‐resistant polymers results from new technological processes requiring higher use temperatures for development. Thermally stable or high performance polymers dictate high melting (softening) temperatures, resistance to oxidative degradation at elevated temperature, resistance to other (nonoxidative) thermolytic processes, and stability to radiation and chemical reagents.

A number of thermally stable polymers have been synthesized, but in general the types of structures that impart thermal resistance also result in poor processing characteristics. Attempts to overcome this problem have largely been concentrated on the incorporation of flexible groups into the backbone or the attachment of stable pendent groups. Among the class of polymers claimed to be thermally stable only a few have achieved technological importance, some of which are polyamides, polyimides, polyquinoxalines, polyquinolines, and polybenzimidazoles. Of these, polyimides have been the most widely explored.
Heat‐Exchange Technology, Heat Transfer
Authors: Cho Young I. , Cho S. M.
Published: July 2004

In order to select a proper heat exchanger for a given application, various factors such as pressure, temperature, size, fouling factor, and the use of toxic or corrosive fluids must be considered. These pressure and temperature requirements mainly dictate the type of heat exchanger selected. In general, for high pressures and temperatures, tubular heat exchangers that conform to safety regulations and manufacturing codes are used. For moderate pressures, small but very efficient plate heat exchangers can be employed.

There are three heat‐transfer modes, ie, conduction, convection, and radiation, each of which may play a role in the selection of a heat exchanger for a particular application. The basic design principles of heat exchangers are also important, as are the analysis methods employed to determine the right size heat exchanger. The shell‐and‐tube exchanger is the workhorse of power, chemical, refining, and other industries. Plate heat exchangers are used as an alternative in relatively low temperature and pressure applications involving liquids and two‐phase flows. Cold‐plate heat exchangers are used for electronics cooling applications.

Heat exchangers are used whenever energy has to be transferred, and the proper design and use of heat exchangers are vitally important for efficient operation of an industrial system, for energy conservation, and ultimately for the protection of the environment. There are numerous design and operating problems originating from a lack of understanding of basic flows and heat‐transfer phenomena such as flow distribution in manifolds, flow‐induced vibration in two‐phase flows, heat‐transfer enhancement, fouling, etc.

In order to help companies and organizations overcome problems associated with heat exchangers, for example, Heat Transfer Research Inc. (HTRI) (U.S) and the Heat Transfer and Fluid Flow Service (HTFS) (UK) provide results of heat‐transfer and fluid‐flow research, design methods, supporting computer programs, and proprietary equipment testing.
Heat‐Exchange Technology, Nonaqueous Heat‐Transfer Media
Authors: Minton Paul E.
Published: July 2004

At temperatures below 0°C or above 200°C, heat‐transfer media other than water often are the more optimum choice. Glycol/water, typically ethylene glycol or propylene glycol solutions, are widely used for liquid‐phase secondary cooling and heating applications. Using appropriate inhibitors, the glycol‐based fluids can be used over a temperature range of −50 to 175°C. Glycol/water solutions intended for heat‐transfer systems are manufactured by Union Carbide Corp. and Dow Chemical.
Herbicides
Authors: Bradow Judith M. , Dionigi Christopher P. , Johnson Richard M. , Wojkowski Suhad
Published: July 2004

Weeds, ie, unwanted plants, reduce crop yields and quality. Of the many approaches used to control weeds, the use of chemical herbicides is considered the most effective and efficient. Herbicides are a critical factor in agricultural productivity and represent a significant economic input in crop production. In the United States, over 280 million kilograms of herbicide are applied annually. This review discusses herbicide mode of action, environmental fate, and chemistry, as well as the historical perspectives and future trends in herbicide development. Topics addressed include analytical methods, allelopathy and natural products, biological control, carcinogenicity, herbicide degradation, leaching, sorption, volatilization, movement in soil, enzyme and biosynthesis inhibition, free radical induction, photosynthesis and pigment bleaching, plant growth regulators, seed safeners, water quality, and weed seeds. Primary herbicide groups include acid amides, amino acid analogues, aliphatic carboxylic acids, benzonitriles, bipyridiniums, carbamates, dinitroanilines, diphenyl ethers, imidazoles, inorganic and metallorganic compounds, mycoherbicides, phenoxy acids, phenoxyalkanoic acids, pyridines, pyridazones, phthalics, sulfonylureas, thiocarbamates, triazines, and ureas. Miscellaneous herbicides include acrolein, cinmethylin, clethodim, clomazone, ethofumesate, sethoxydim, and tridiphane. A list of herbicide, agrichemical, and toxicology databases is provided.
Polyethylene, High Density
Authors: Kissin Yury V.
Published: July 2004

High density polyethylene (HDPE) is a product of ethylene polymerization with a density of 0.940 g/cm3or higher. HDPE resins include both homopolymers of ethylene and its copolymers with α‐olefins. HDPE resins include a large variety of products that differ in molecular weight, molecular weight distribution, and density; they are produced with several classes of catalysts: Phillips catalysts based on chromium oxides, catalysts containing chromium complexes, Ziegler catalysts based on titanium or vanadium compounds, and, in some special cases, metallocene catalysts. Two of the most important industrial processes for manufacturing HDPE are polymerization in a slurry and gas‐phase polymerization.

HDPE is one of the largest volume commodity plastics produced in the world, with a worldwide capacity in 1994 of over\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${14\times 10^{6}{\hskip0.167em}{\hskip0.167em}{\rm{t}}/{\rm{yr}}}$\end{document}. Blow‐molded products represent the biggest use for HDPE resins. They also used for bottles, housewares, toys, pails, drums, tanks, and other similar products. Injection‐molding products are the second largest application; they include housewares, toys, food containers, pails, crates, and cases. HDPE is also used for film manufacture, pipes of various diameters, wire and cable coatings, and foam. Low molecular weight HDPE waxes are used for paper coatings, spray coatings, emulsions, and in printing inks. High molecular weight HDPE is a specialty plastic with a high impact strength and abrasion resistance; it is used in such industrial applications as chemical and mineral processing, electrical equipment, municipal plants, and medical implants. High strength fibers produced with this polymer are used in bullet‐proof jackets and armor.
Hormones, Human Growth Hormone
Authors: Becker Gerald W. , MacKellar Warren C. , Riggin Ralph M. , Wroblewski Victor J.
Published: July 2004

Human growth hormone (hGH), a protein hormone produced and secreted by the somatotropic cells of the anterior pituitary, plays a key role in somatic growth through its effects on the metabolism of proteins, carbohydrates, and lipids. The biological properties of hGH are diverse and complex, with the molecule exhibiting anabolic activity, insulin‐like and diabetogenic activities, and lactogenic activity, as well as producing effects on water and salt retention. First isolated from the pituitary gland, hGH is produced using recombinant DNA technology and has been approved for use as a human pharmaceutical in the treatment of growth failure owing to hGH deficiency and in the treatment of Turner's syndrome in Europe and Japan. In addition, hGH is being investigated for use in treating burns, various wounds, osteoporosis, cachexia, and other conditions. Human growth hormone is one of the largest selling therapeutic proteins produced by recombinant DNA technology.
Hydantoin and Its Derivatives
Authors: Avendaño Carmen , Menendez J. Carlos
Published: July 2004

Hydantoins are a group of closely related substances for which several general patterns regarding their physical properties, chemical reactivity, synthesis, and analysis can be found. Physical properties of hydantoin derivatives, including melting point and ionization properties, are discussed in terms of their relationship with molecular association through hydrogen bonds. A survey of their spectral properties (uv, ir, nmr, luminescence, and mass spectra) is also given. Treatment of chemical reactivity is descriptive, with little or no emphasis on mechanistic aspects. The most common synthetic and analytical methods are also briefly discussed. Medicinal applications are commented on and various other industrial applications of hydantoins are also covered.
Hydrogen
Authors: Baade William F. , Parekh Uday N. , Raman Venkat S.
Published: July 2004

Hydrogen is one of the most important industrial commodities. Physical thermodynamic, and chemical properties are described. The chemistry of hydrogen from a commercial perspective is followed by a description of manufacturing methods. Steam reforming of hydrocarbons and partial oxidiation of hydrocarbons account for almost all hydrogen production. Other, less conventional manufacturing methods are also presented, such as produced as a by‐product of chemical processes. Hydrogen purification is reviewed. The storage of hydrogen is discussed, including conventional methods for gas and liquid storage, and possible future methods, such as in metal hydride systems and microcapsules. Analysis of hydrogen, specifications health and safety issues, recycling, and environmental considerations are discussed. Hydrogen consumption figures are presented, and the possible future usage of hydrogen is discussed.
Hydroxycarboxylic Acids
Authors: Datta Rathin
Published: July 2004

Hydroxycarboxylic acids are an important group of chemicals, with several members that are commercially manufactured in large volumes and have a wide range of applications. Two α‐hydroxycarboxylic acids, lactic and glycolic, and a derivative of γ‐hydroxycarboxylic acid γ‐butyrolactone are discussed in detail because of their relative commercial importance, both current and future. General classes of reactions that these acids undergo are also discussed, with specific examples of those reactions that are or could become commercially important.

Current manufacturing processes for lactic and glycolic acids and γ‐butyrolactone are briefly outlined, with estimates of the production volume and market size for various applications. For lactic acid production and manufacture of its derivatives for biodegradable polymers, new processes are emerging, and some of the recent patents and emerging technologies are highlighted. Some of the important uses of hydroxycarboxylic acids are related to environmentally friendly products and processes such as biodegradable plastics for consumer products and nontoxic and easily degradable solvents, cleaning agents, plasticizers, etc. The emergence of new technologies for efficient and economical manufacture of these chemicals, combined with these product opportunities, could make these hydroxycarboxylic acids very large‐volume chemicals of global commercial importance.
Hydrothermal Processing
Authors: Dawson William J. , Krijgsman Pieter
Published: July 2004

Hydrothermal processing encompasses a broad set of technologies that share a range of operating temperatures and pressures and require the use of engineered pressure systems. Technologies include pressure leaching and precipitation reactions used in mineral recovery, hydrothermal synthesis for manufacture of fine oxide powders, hydrothermal crystallization of α‐quartz and other large crystals, wet oxidation for treatment of organic sludges, and supercritical water oxidation for destruction of hazardous organic wastes. Development and utilization of hydrothermal processes are described including the use of hydrothermal synthesis for zeolites, electronic ceramics, magnetics, inorganic pigments, and silicates. A description of process systems and equipment is given.
Hydraulic Fluids
Authors: Denniston Alan D.
Published: July 2004

Hydraulic power utilizes hydraulic fluids which may be based on mineral oils, fire‐resistant fluids, high water‐base fluids, water‐in‐oil emulsions, oil‐in‐water emulsions, synthetic fluids, synthetic lubricants, olefin oligimers, alkylated aromatics, polybutenes, cycloaliphatics, diesters, polyol esters, polyglycols, phosphate esters, silicones, silicate esters, or halogenated fluids. These fluids are discussed.

Most fluids require additives which act as pour‐point depressants, viscosity index improvers, defoamers, antioxidants, corrosion and rust inhibitors, and/or anti‐wear compounds. Hydraulic fluids basically serve as lubricants to the hydraulic system utilized. Industries employing hydraulic systems include transportation, manufacturing, mining, metal foundries, agriculture, and timber.
Hydrogen‐Ion Activity
Authors: Durst Richard A. , Bates Roger G.
Published: July 2004

Hydrogen ions are involved in a wide variety of chemical and biochemical reactions, the equilibria and kinetics of which are directly affected by the activity of these ions. This activity, expressed in terms of pH, is therefore of fundamental importance in many areas of science and technology; the determination of pH is one of the most widely performed analytical measurements, ranging in application from research and clinical laboratories to monitoring industrial processes.

Of the two methods for measuring pH, electrometric and chemical indicator (optical), the most common is based on the pH glass electrode used in combination with a reference electrode and pH meter. The indicator method, using pH‐sensitive dyes, can be combined with optical readout devices, such as fiber optics and photometers, or simply by visual color comparison. The pH scale is defined by a series of reference buffer solutions which are used to calibrate the pH measurement system. Although pH measurements are among the most specific with respect to possible interferences, there are a number of potential sources of error that can affect the accuracy of the measurements. These errors, which include fouling of the electrodes, flow variations, suspended matter, temperature variation, and dehydration of the glass membrane in nonaqueous media, are discussed.
Hydroquinone, Resorcinol, and Catechol
Authors: KRUMENACKER Léon , Costantini Michel , Pontal P. , Sentenac J.
Published: July 2004

Worldwide manufacturing capacities of hydroquinone, resorcinol, and catechol are 50,000, 30,000, and 25,000 t/y, respectively. Selective processes leading to hydroquinone are achieved by the oxidation of aniline using manganese dioxide or the hydroperoxidation ofpara‐diisopropylbenzene. Selective resorcinol synthesis use alkali fusion of them‐benzenedisulfonic acid and the hydroperoxidation ofm‐diisopropylbenzene. Coproduction of hydroquinone and catechol is based on phenol hydroxylation by hydrogen peroxide. Much research has been devoted to the hydroxylation of phenol by hydrogen peroxide, in order to try to better master the ratio hydroquinone–catechol. In homogeneous catalysis, it has been found that it is possible to favor the formation of hydroquinone using benzaldehydes or benzophenones in conjunction with a strong acid. In the field of heterogeneous catalysis, the discovery of titanium silicalite (a synthetic molecular sieve) allowed phenol conversion up to 20%. In this case, solvent effects can favor the formation of hydroquinone. Numerous syntheses of hydroquinone, resorcinol, and catechol derivatives have been described.
Hydrocarbon Resins
Authors: Lowery R. Derric
Published: July 2004

Hydrocarbon resins are low molecular weight thermoplastic polymers synthesized via the polymerization of coal‐tar fractions, cracked petroleum distillates, terpenes, or pure olefinic monomers. In general, these polymers may be categorized as coumarone–indene, petroleum, or polyterpene resins. Coumarone–indene resins are synthesized from aromatic monomers obtained from the coking of coal. Petroleum distillates, such as piperylenes and styrene, are obtained from the vapor‐phase cracking of light to heavy petroleum naphthas and are used for the production of petroleum resins. Petroleum resins may be grouped into C‐5 aliphatic, C‐5–C‐9 aromatic modified aliphatic, cycloaliphatic diene (dicyclopentadiene), and C‐9 aromatic resins. Polyterpenes are produced from monoterpenic monomers such as limonene and β‐pinene, which are obtained from the citrus and wood industries, respectively. Most coumarone–indene, petroleum, and polyterpene resins are produced by carbocationic polymerization using Lewis acid catalysis. Cycloaliphatic diene‐based resins are typically produced via thermal polymerization techniques. The hydrogenation of hydrocarbon resins is typically accomplished using supported monometallic and bimetallic catalyst systems based on the Group VI and VIII transition elements. Uses and applications for hydrocarbon resins include adhesives, sealants, inks, paints, varnishes, plastics, and oil field applications. They are rarely used alone.
Hydroxybenzaldehydes
Authors: Maliverney Christian , Mulhauser Michel
Published: July 2004

Among the hydroxybenzaldehydes, only mono‐, di‐ and trihydroxybenzaldehydes are known. Salicylaldehyde (2‐hydroxybenzaldehyde) and 4‐hydroxybenzaldehyde represent more than 99% of the hydroxybenzaldehydes' market. The physical and chemical properties of hydroxybenzaldehydes are described. 2‐Hydroxy and 4‐hydroxybenzaldehydes react in a similar manner as phenol toward electrophiles. The aldehyde function can be reduced or oxidized to form a variety of compounds depending on the reagents and conditions used. Hydroxybenzaldehydes undergo the normal reactions of aromatic aldehydes.

Most industrial methods for the manufacture of hydroxybenzaldehydes are based on phenol, but other routes exist, starting from hydroxybenzoic acids, by reduction, or from cresols, by oxidation. Bothp‐hydroxybenzaldehyde and salicylaldehyde have a low to moderate acute oral toxicity, but salicylaldehyde is, in addition, corrosive toward skin and appreciably irritating to the eyes.

The hydroxybenzaldehydes are used primarily as chemical intermediates to a variety of products. The largest single use of salicylaldehyde is in the manufacture of coumarin. Both are used as intermediates in the synthesis of agrochemicals, pharmaceuticals, fragrances, and in electroplating. Condensation products of salicylaldehyde and diamines have important chelation properties, and have wide use in the stabilization of petroleum products, and in chemical processing, especially as oxidation catalysts. These and other applications to polymer chemistry are described.
Hydrazine and Its Derivatives
Authors: Schiessl Henry W.
Published: July 2004

Hydrazine (diamide), N2H4, a colorless liquid having an ammoniacal odor, is the simplest diamine and unique in its class because of the N—N bond.

Hydrazine and its simple methyl and dimethyl derivatives have endothermic heats of formation and high heats of combustion. Hence these compounds are used as rocket fuels. Other derivatives are used as gas generators and explosives. Hydrazine, a base slightly weaker than ammonia, forms a series of useful salts. As a strong reducing agent, hydrazine is used for corrosion control in boilers and hot‐water heating systems; also for metal plating, reduction of noble‐metal catalysts, and hydrogenation of unsaturated bonds in organic compounds. Hydrazine is also an oxidizing agent under suitable conditions. Having two active nucleophilic nitrogens and four replaceable hydrogens, hydrazine is the starting material for many derivatives, among them foaming agents for plastics, antioxidants, polymers, polymer cross‐linkers and chain‐extenders, as well as fungicides, herbicides, plant‐growth regulators, and pharmaceuticals. Hydrazine is also a good ligand; numerous complexes have been studied. Many heterocyclics are based on hydrazine, where the rings contain from one to four nitrogen atoms as well as other heteroatoms.

The many advantageous properties of hydrazine assure continued‐commercial utility. Hydrazine is available in anhydrous form as well as aqueous solutions, typically 35, 51.2, 54.4, and 64 wt % N2H4(54.7, 80, 85, and 100% hydrazine hydrate).

The commercially feasible processes involve partial oxidation of ammonia (or urea) using hypochlorite or hydrogen peroxide. Most hydrazine is produced by some variation of the Raschig process, which is based on the oxidation of ammonia using alkaline hypochlorite.

Hydrazine is toxic and readily absorbed by oral, dermal, or inhalation routes of exposure.
Hydroboration
Authors: Zaidlewicz Marek
Published: July 2004

The hydroboration reaction and transformations of its organoborane products are described. The mechanism and the chemo‐, regio‐, and stereoselectivity of the hydroboration reaction are presented, as well as the synthesis and characteristics of the most common hydroborating agents. Transformations of organoboranes may involve carbon‐hetero atom bond formation and lead to stereoselective synthesis of organic halides, amines, aziridines, sulfur, selenium, and mercury compounds. Hydroboration‐protonolysis is a nonocatalytic method of cis‐hydrogenation of multiple bonds. Hydroboration‐oxidation is a standard method for cis‐anti‐Markovnikov hydroxylation of multiple bonds.

Carbon‐carbon bond formation can be accomplished by transformation of organoboranes through coupling of groups attached to boron, cross‐coupling of organoboranes with organic halides, organoborate rearrangements providing access to alkynes, (E)‐ and (Z)‐alkenes, (E,E)‐, (E,Z)‐, (Z,Z)‐dienes, and enynes. Single‐carbon insertion reactions include carbonylation, cyanidation, and the DCME and related reactions. Other reactions include α‐ and β‐alkylation of carbonyl compounds, the addition of alkynyl, alkenyl, and allylic boranes to aldehydes, leading to proparylic alcohols and stereodefined allylic and homoallylic alcohols, boron‐stabilized carbanions, the boron Wittig reaction, and concerted reactions of allylic and vinylic boranes. Contrathermodynamic isomerization of olefins is discussed. The synthesis of boron‐containing polymers and of isotopically labeled compounds is covered. Asymmetric synthesis via chiral organoboranes is covered in detail.
Hypnotics, Sedatives, Anticonvulsants, and Anxiolytics
Authors: Williams Michael , Holladay Mark W.
Published: July 2004

Compounds that are clinically used as hypnotics, sedatives, anxiolytics, and anticonvulsants share a spectrum of related activities that may reflect a common molecular substrate within the brain. The alcohols, benzodiazepines, and barbiturates represent the principal classes of compounds reviewed. Whereas the mode of action of a number of hypnotics, sedatives, and anxiolytics is known, many agents used as anticonvulsant agents act by unknown mechanisms and as a result have considerable side effect liabilities. Newer agents including γ‐aminobutyric acid (GABA) modulators, glutamate andN‐methyl‐D‐aspartate acid (NMDA)‐receptor antagonists, nonbenzodiazepine ligands for the central benzodiazepine (BZ)receptor, and a variety of miscellaneous agents including CCK‐A receptor antagonists (CI‐988) and 5HT receptor modulators are also discussed.
Immunotherapeutic Agents
Authors: Wong Stewart
Published: July 2004

Immunotherapeutic agents are used in treatment of primary immunodeficiencies as well as those immune system aberrations resulting from other diseases. A number of natural and synthetic agents have been discovered that can modulate components of the immune system. Furthermore, cytokines, such as interleukins, and immune cells having specific markers, such as antibodies, continue to be defined, leading to a complex although incomplete picture of immune responses. The immune system and its responses are discussed.

Immunomodulators that play a role in the treatment of acquired immune deficiency syndrome as well as those used in therapy for rheumatoid arthritis, an autoimmune dysfunction, are described. Immunosuppressants used in anticancer therapy and organ transplants are presented.
Lead Compounds, Industrial Toxicology
Authors: DeVito Stephen C. , Breen Joseph
Published: July 2004

Lead is toxic to the kidney, cardiovascular system, developing red blood cells, peripheral and central nervous systems, testes, and fetus. Exposure to lead may occur from a variety of occupational and nonoccupational sources. Although in the United States regulatory and voluntary efforts have been quite successful in reducing worker and population exposure to lead, over two million workers remain at risk of workplace lead exposure. The concern for lead as a significant public health problem has increased as evidence has mounted regarding adverse health effects at successively lower levels of lead exposure, leading to downward revision of criteria for acceptable blood lead concentrations. Exposure, toxicity, and detection of lead in humans is discussed as is the treatment of lead poisoning.
Water, Industrial Water Treatment
Authors: Robinson James
Published: July 2004

Abundant supplies of fresh water are essential to the development of industry. Enormous quantities are required for the cooling of products and equipment, for process needs, for boiler feed, and for sanitary and potable water supply. This article gives details on the various impurities found in water and how the water is treated to make it acceptable for industrial use. Clarification, precipitation, settling, filtration, ion exchange, and membrane processes are all detailed. Particular attention is given to corrosion control in boilers. Condensate systems can be chemically treated to reduce metal corrosion, especially important in cooling systems. Types of corrosion, eg, pitting, galvanic corrosion, are discussed. Deposit accumulations in cooling systems, biofouling and microfouling organisms are also summarized.
Information Retrieval
Authors: Barcelon‐Yang Cynthia S. , Brownlee Evelyn L. , Calhoun Emmett D. , Caputo Bruno A. , Cumbo Charles C. , Daniszewski Joseph P. , Eckel Douglas A. , Glaspey Kenneth H. , Green‐Kocher Darlyn C. , Gruber Marianne B. , Isselmann Margaret M. , Johns Thomas C. , King Alicia P. , Krentz David M. , Kvalnes Florence H. , Minkiewicz Luray M. , Nazer Behrooz , Parsons Angela K.G , Perrotto Carol R. , Ratliff Rita D. , Sikes Jeanette C. , Webster Amie H.
Published: July 2004

Different on‐line database resources are described. Database producers and vendors are defined, and a summary of available technical and business chemical databases presented. Scientists dealing with chemicals have the advantage that a chemical structure is a unique presentation. Regardless of their languages, researchers in Japan or in New Zealand will have the same understanding of a chemical structure. A number of sections in this article deal with this unique characteristic of chemistry. Searching for structures using the Chemical Abstract Registry Number, which represents a chemical structure in files such as Registry, Beilstein, and DARC is described. Another challenge to searchers in finding specific physical data is addressed in Numeric, Spectra, and Reaction sections. Patents have significant influence in providing funds to researchers by both industrial and academic sectors. Available databases are discussed and information regarding both on‐line and CD‐ROM presented. Environmental and safety aspects of chemicals in our daily life are taking a predominate role and available on‐line and private information is discussed. Other resources to aid individuals in dealing with searching and storing data are discussed.
Infrared Technology
Authors: Jones Roger W.
Published: July 2004

The ir region of the electromagnetic spectrum is important because every material object emits, absorbs, transmits, and reflects ir radiation in a characteristic manner. Two kinds of information can be gathered from the radiation after it has interacted with the object. Spectrometry determines the chemical composition of the object; radiometry determines the object's thermal characteristics. The basic principles and practices of both spectrometry and radiometry (including thermal imaging) in the ir region are reviewed. The sampling modes used in the spectrometry techniques of transmission, specular reflection, diffuse reflection, attenuated total reflection, photoacoustic absorption, emission, microspectroscopy, and open‐path sampling are examined, and the methods for analyzing and interpreting data are discussed. Uses of spectrometry, including process line monitoring, defect analysis, environmental monitoring, and weathering studies, as applied in the polymer, pharmaceutical, grain, food, and flavor and fragrance industries are reviewed. The relations among temperature, emittance, radiance, and radiometric measurement are summarized. Using the medium‐wave and long‐wave regions of the ir spectrum for radiometry are compared. Applications of radiometry and thermal imaging to process monitoring, plant maintenance, nondestructive evaluation, and stress analysis are discussed. The characteristics of ir optical materials, fibers, sources, detectors, radiometers, thermal imagers, and spectrometers (grating, Fourier transform, interference filter, and acousto‐optic filter) are reviewed. Vol. 14, pp. 379–416, 85 refs. to June 1993.
Inks
Authors: Bassemir R. W. , Bean A. , Wasilewski O. , Kline D. , Hillis W. , Su C. , Steel I. R. , Rusterholz W. E.
Published: July 2004

This article includes a description of the important commercial printing processes used in the world. The inks required for each of these processes are described, including the key ingredients in the formula necessary due to the physical constraints of each particular printing process. A discussion of the nature of the raw materials used in printing inks and their general chemical composition is given. A summary of the environmental regulations applying to the printing industry and their impact on ink formulation is presented.