bluuebunny/crossref_metadata_2025 huggingface dataset:
Edna Millay, Muriel Rukeyser, and Adrienne Rich: political poetry, social protest, and the place of the woman writer
Authors: Michailidou Artemis
Published: August 2004

This paper will analyze primarily the impact of Edna St. Vincent Millay’s political writing on Adrienne Rich, and address the relationship between Millay and Muriel Rukeyser. Through close examination of these women’s concept of the ‘political’ poet, as well
as their attitudes toward socially conscious writing, I will try to show that Millay’s influence extends to areas that have repeatedly been bypassed (or approached only superfi- cially), and argue that the earlier poet played an instrumental role in the formation of the younger artist’s
social consciousness. By evaluating the range and degree of Millay’s influence, I will also demonstrate that the earlier poet was among those figures who helped Adrienne Rich to both crystallize her views regarding ‘proper’ literary models and argue for a female tradition
that would recognize the importance of versatility and experimentation practised by writers such as Millay.
Unknown social identities: Spanish guerrillas in the Peninsular War, 1808–14
Authors: Fraser Ronald
Published: August 2004

Few aspects of the Peninsular War have been, and remain, more controversial among Spanish, French and British historians than the Spanish guerrilla. National perceptions, pride, prejudice and romantic mythology colour many an argument which in consequence does not greatly advance
our knowledge. In an attempt to shift the debate onto a more solid socio-historical ground, the author initiated and directed the construction of two databases - one of 748 guerrilleros, the other of 343 persons who were sentenced to death as guerrilleros or bandits by the Bonapartist regime’s
special courts, the so-called Juntas Criminales. The following essay uses material from these to study the guerrilleros’ social origins, a first step in the wider study of the guerrilla movement for a forthcoming book on the Spanish people’s role in the Peninsular War.
The role of metformin in the treatment of infertile women with polycystic ovary syndrome
Authors: Atiomo William , Sinha Anju
Published: August 2004

Polycystic ovary syndrome (PCOS) is the most common cause of anovulatory infertility and is conventionally treated with clomifene. Recent research shows that insulin resistance and hyperinsulinaemia lead to hyperandrogenism in PCOS. It is thought that this causes anovulation and infertility and is the rationale for the use of insulin‐sensitising drugs such as metformin. This article explores the role of metformin, which is being increasingly used as first‐line therapy to treat infertility with PCOS and potentially avoids the risks of multiple pregnancy and ovarian hyperstimulation associated with clomifene.
Avoiding pregnancy at the time of sterilisation
Authors: Roberts Nicole Julia , Argent Vincent P
Published: August 2004

This article will address the risk management issues surrounding a pre‐existing pregnancy at the time of female sterilisation. It will concentrate on risk avoidance through counselling and issues of consent, as well as illustrating a number of important precautions that can be taken to reduce the risk of complications occurring. The investigation and analysis of confirmed pregnancies and those at risk of a pre‐existing pregnancy will also be discussed. Good practice, careful documentation and adherence to guidelines by healthcare professionals may help reduce the large number of medico‐legal claims arising from female sterilisation.
Effective assessment of trainees
Authors: Shaw Laurence MA
Published: August 2004

In educational terms, assessment should be a reliable, objective measure of our knowledge and abilities. Learning can be divided into different areas which, in educational terms, are called ‘domains’. These comprise knowledge, attitude to learning and skills. Each domain requires a different type of assessment. This article looks at how these areas of learning can be assessed in terms of medical education.
Overseas trainees in obstetrics and gynaecology in the UK
Authors: Habbu Jyoti , Nanal Rashmi , James Mark
Published: August 2004

Overseas trainees have travelled to gain experience in the UK for many years. The Royal College of Obstetricians and Gynaecologists maintains close ties with its overseas members in order to continue the historical links that provide doctors with training and service provision. In recent years, changes have affected the training opportunities available. This article provides practical advice and a guide to training within the UK. In addition, there is practical advice to overseas trainees who are considering this as an option.
Acetone
Authors: Howard William L.
Published: August 2004

Acetone (2‐propanone, dimethyl ketone, CH3COCH3), molecular weight 58.08 (C3H6O), is the simplest and most important of the ketones. It is a colorless, mobile, flammable liquid and is miscible in all proportions with water and most organic solvents. It is used in the manufacture of a variety of coatings and plastics and as a raw material for the chemical synthesis of a wide range of products such as ketene, methyl methacrylate, and bisphenol A. Most manufactured acetone is obtained as a coproduct in the process for phenol from cumene. Numerous natural sources of acetone make it a normal constituent of the environment. It is readily biodegradable. Acetone shows the typical reactions of saturated aliphatic ketones and is among the solvents of comparatively low acute and chronic toxicity.
Acetic Anhydride
Authors: Wagner Frank S.
Published: August 2004

Acetic anhydride (CH3CO)2O, is a mobile, colorless liquid that has an acrid odor. It is the largest commercially produced carboxylic acid anhydride. Its chief industrial application is for acetylation reactions, and it is also used in many other applications in organic synthesis. Manufacturing processes include the acetic acid process, the acetaldehyde oxidation process, and methyl acetate carbonylation. Acetic anhydride penetrates the skin, forming burns and blisters.
Acrylamide Polymers
Authors: Lipp David , Kozakiewicz Joseph
Published: August 2004

Acrylamide polymerizes in the presence of free‐radical initiators to form polyacrylamide chains. Acrylamide polymers include functionalized polymers prepared from polyacrylamide by postreaction and copolymers prepared by polymerizing acrylamide (2‐propenamide, C3N5NO) with one or more comonomers. Completely dry polyacrylamide is a brittle white solid. Polyacrylamide is soluble in water, and high molecular weight polyacrylamide forms viscous homogeneous solutions in it. Reactions include hydrolysis, sulfomethylation, methylol formation, and reaction with other aldehydes. Most uses for high molecular weight polyacrylamides in water treating, mineral processing, and paper manufacture are based on the ability of these polymers to flocculate small suspended particles by charge neutralization and bridging. Low molecular weight polymers are employed as dispersants, crystal growth modifiers, or selective mineral depressants.
Aluminum Oxide (Alumina), Activated
Authors: Pearson Alan
Published: August 2004

The activated aluminas comprise a series of nonequilibrium forms of partially hydroxylated aluminum oxide, Al2O3. The chemical composition can be represented by\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{Al}}{_{2}}{\rm{O}}_{{(}3-x{)}}}$\end{document}(OH)2xwherexranges from about 0 to 0.8. They are porous solids made by thermal treatment of aluminum hydroxide precursors and find application mainly as adsorbents, catalysts, and catalyst supports. Activated alumina, for purposes of this discussion, refers to thermal decomposition products (excluding α‐alumina) of aluminum trihydroxides, oxide hydroxides, and nonstoichiometric gelatinous hydroxides. The term “activation” is used to indicate a change in properties resulting from heating (calcining). In general, as a hydrous alumina precursor is heated, hydroxyl groups are driven off, leaving a porous solid structure of activated alumina. The physical properties of the material are set by the choice of precursor, the forming process, and the activation conditions. Activated alumina is a relatively innocuous material from a health and safety standpoint. It is nonflammable and nontoxic. Normal precautions associated with handling of nuisance dusts should be taken. Activated alumina is normally shipped in moisture‐proof containers because of its strong desiccating action.
Aluminates
Authors: Keller Robert J. , Len Joseph J.
Published: August 2004

Among industrial users of sodium aluminate are producers of paper, paint pigments, silica, alumina or alumina‐based catalysts, dishwasher detergents, molecular sieves, concrete, antacids, and others. Sodium aluminate is used in removal of phosphates from municipal and industrial waste waters and for clarification of industrial process and potable water. Commercial sodium aluminate products are available as liquids, and to a lesser degree, in solid form. The formula of anhydrous sodium aluminate is variously given as NaAlO2(aluminum sodium oxide),\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{Na}}{_{2}}{\rm{O}} {\rm{{\cdot{}}}}{\rm{Al}}{_{2}}{\rm{O}}{_{3}}}$\end{document}, or Na2Al2O4. Commercial sodium aluminates are not accurately represented by these formulas because the products contain more than the stoichiometric amount of sodium oxide, Na2O. The amount of excess caustic in commercial products is indicated by ratios of Na2O/Al2O3. Commercial quantities of sodium aluminate are made from hydrated alumina, in the form of aluminum hydroxy oxide, AlO(OH), or aluminum hydroxide, Al(OH)3, a product of the Bayer process which is used to refine bauxite, the principal aluminum ore. In addition to treatment of industrial and municipal water supplies, sodium aluminate is used in large quantities in papermaking where it improves sizing, filler retention, and pitch deposition. Sodium aluminate is also widely used in the preparation of alumina‐based catalysts.
Amines, Aromatic, Aniline and Its Derivatives
Authors: Amini Bijan
Published: August 2004

Aniline (benzenamine) is the simplest of the primary aromatic amines. Aromatic amines can be produced by reduction of the corresponding nitro compound, the ammonolysis of an aromatic halide or phenol, and by direct amination of the aromatic ring. At present, the catalytic reduction of nitrobenzene is the predominant process for manufacture of aniline. Pure, freshly distilled aniline is a colorless, oily liquid that darkens on exposure to light and air. It has a characteristic sweet, amine‐like aromatic odor. Aniline is miscible with acetone, ethanol, diethyl ether, and benzene, and is soluble in most organic solvents. Aromatic amines are usually weaker bases than aliphatic amines. Aromatic amines form addition compounds and complexes with many inorganic substances, such as zinc chloride, copper chloride, uranium tetrachloride, or boron trifluoride. Various metals react with the amino group to form metal anilides; and hydrochloric, sulfuric, or phosphoric acid salts of aniline are important intermediates in the dye industry. Important reactions include
n
‐alkylation, ring alkylation, acylation, condensation, cyclization, reaction with nitrous acid, oxidation, halogenation, sulfonation, nitration, and reduction. The predominant process for manufacture of aniline is the catalytic reduction of nitrobenzene with hydrogen. The flash point of aniline (70°C) is well above its normal storage temperature, but aniline should be stored and used in areas with minimum fire hazard. Aniline is slightly corrosive to some metals. It attacks copper, brass, and other copper alloys, and use of these metals should be avoided in equipment that is used to handle aniline. Aniline is shipped in tank truck and tank car quantities and is classified by the U.S. Department of Transportation (DOT) as a Class B poison (UN 1547), and must carry a poison label. Wastes contaminated with aniline may be listed as RCRA Hazardous Waste. Aniline is highly toxic and may be fatal if swallowed, inhaled, or absorbed through the skin. Aniline vapor is mildly irritating to the eye, and in liquid form it can be a severe eye irritant and cause corneal damage. The U.S. Department of Labor (OSHA) has ruled that an employee's exposure to aniline in an 8‐h work shift of a 40‐h work week shall not exceed an 8‐h time‐weighted average (TWA) of 5 ppm vapor in air. Based on tests with laboratory animals, aniline may cause cancer. Aniline should be handled in areas with adequate ventilation and skin exposure should be avoided by the wearing of proper safety equipment. The major uses of aniline are in the manufacture of polymers, rubber, agricultural chemicals, dyes and pigments, pharmaceuticals, and photographic chemicals. Most derivatives of aniline are prepared by hydrogenation of their nitroaromatic precursors.
Barium
Authors: Boffito Claudio
Published: August 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‐earth 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 which accounts for its principal uses as a getter for removing residual gases from vacuum systems 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 in commercial production. Barium has a bcc crystal structure at atmospheric pressure, but undergoes solid‐state phase transformations at high pressures. Because of such transformations, barium exhibits pressure‐induced superconductivity at sufficiently low temperatures. Barium has a valence electron configuration of 6
s
2
and characteristically forms divalent compounds. 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.
Benzaldehyde
Authors: Opgrande Jarl L. , Dobratz C. J. , Brown Edward , Liang Jason , Conn Gregory S. , Shelton Frederick J. , With Jan
Published: August 2004

Benzaldehyde, C
6
H
5
CHO, is the simplest and possibly the most industrially useful member of the family of aromatic aldehydes. Benzaldehyde exists in nature, primarily in combined forms such as a glycoside in almond, apricot, cherry, and peach seeds. The characteristic benzaldehyde odor of oil of bitter almond occurs because of trace amounts of free benzaldehyde formed by hydrolysis of the glycoside amygdalin. Benzaldehyde is a versatile intermediate because of its reactive aldehyde hydrogen, its carbonyl group, and the benzene ring. The only industrially important processes for the manufacturing of synthetic benzaldehyde involve the hydrolysis of benzal chloride and the air oxidation of toluene. The hydrolysis of benzal chloride is no longer utilized in the United States. Benzaldehyde is produced in the United States by Kalama Chemical Incorporated, Kalama, Washington. Benzaldehyde is sold as technical grade or as meeting the specifications of the
National Formulary
(NF), the
Food Chemicals Codex
(FCC), or the
British Pharmacopeia
(BP). The oral LD
50
for benzaldehyde is reported as 1300 mg/kg in rats and as 1000 mg/kg in guinea pigs. Based upon these values, benzaldehyde is considered a moderately toxic substance when ingested. Overexposure to benzaldehyde vapors is irritating to the upper respiratory tract and produces central nervous system depression, with respiratory failure possible. The low autoignition temperature of benzaldehyde (192°) presents safety problems. Benzaldehyde may also spontaneously ignite when soaked into rags or clothing or adsorbed onto activated carbon. Bulk storage of benzaldehyde should be made under a nitrogen blanket. Benzaldehyde is a synthetic flavoring substance, sanctioned by the U.S. Food and Drug Administration (FDA) to be generally recognized as safe (GRAS) for foods. Both “pure almond extract” and “imitation almond extract” are offered for sale; each contains 2.0–2.5 wt % benzaldehyde. Benzaldehyde is also recognized as safe for use as a bee repellant in the harvesting of honey. Benzaldehyde's most important use is in organic synthesis, where it is the raw material utilized to produce various aldehydes.
Aeration, Biotechnology
Authors: Nienow Alvin W.
Published: August 2004

The supply of oxygen to a growing biological species, aeration, in aerobic bioreactors is one of the most critical requirements in biotechnology. Aeration is usually accomplished by transferring oxygen from the air into the fluid surrounding the biological species, from where it is in turn transferred to the biological species itself. During the course of a batch bioreaction, oxygen demand often passes through a marked maximum when the species is most biologically active. The main reason for the importance of aeration lies in the limited solubility of oxygen in water. The basic principles which underlie oxygenation (aeration) are exactly the same as those which determine the rate of transfer of any sparingly soluble gas (oxygen) from the gas stream (air) to the unsaturated liquid (broth). The rate at which this transfer takes place is dependent on the area of contact between the gas and the liquid, the driving force available (ie, the difference in concentration of oxygen in the two phases), the two‐phase fluid dynamics, and the chemical composition of the liquid. A huge variety of bioreactors has been developed; a useful subdivision has been made into three generic types. These are bioreactors driven by rotating agitators (stirred tanks), bioreactors driven by gas compression (bubble columns/loop fermenters), and bioreactors driven by circulating liquid (jet loop reactors). Aeration is used in mycelial fermentation, xanthan gum fermentation, mammalian and plant cell culture, single‐cell protein, and biological aerobic wastewater treatment.
Boron Halides
Authors: Alam Fazlul
Published: August 2004

The boron trihalides boron trifluoride, BF3, boron trichloride, BCl3, and boron tribromide, BBr3, are important industrial chemicals having increased usage as Lewis acid catalysts and in chemical vapor deposition (CVD) processes. Boron halides are widely used in the laboratory as catalysts and reagents in numerous types of organic reactions and as starting material for many organoboron and inorganic boron compounds. Reactions of boron trihalides that are of commercial importance are those of BCl3and, to a lesser extent, BBr3, with gases in chemical vapor deposition (CVD). Boron trichloride is prepared on a large scale by the reaction of Cl2and a heated mixture of borax,\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{Na}}{_{2}}{\rm{BO}}_{4}{\rm{O}}{_{7}}{\hskip-0.167em}{\hskip-0.167em}{\cdot{}}{\hskip-0.167em}{\hskip-0.167em}10{\rm{H}}{_{2}}{\rm{O}}}$\end{document}, and crude oil residue in a rotary kiln heated to 1038°C. Boron trihalides, BX3, are trigonal planar molecules which are (sp)2hybridized. The X–B–X angles are 120°. The boron trihalides are strong Lewis acids; however, the order of relative acid strengths,\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{BI}}{_{3}}\geq {\rm{BBr}}{_{3}}>{\rm{BCl}}{_{3}}>{\rm{BF}}{_{3}}}$\end{document}, is contrary to that expected based on the electronegativities and atomic sizes of the halogen atoms. Boron tribromide is produced on a large scale by the reaction of Br2and granulated B4C at 850–1000°C or by the reaction of HBr with CaB6at high temperatures. Approximately 75–95% of the BCl3consumed in the United States is used to prepare boron filaments by CVD. Another important use of BCl3is as a Friedel‐Crafts catalyst in various polymerization, alkylation, and acylation reactions, and in other organic syntheses. BCl3is also used for the production of halosilanes, in the preparation of many boron compounds and in the production of optical wave guides. Approximately 30% of BBr3produced in the United States is consumed in the manufacture of proprietory pharmaceuticals. BBr3is used in the manufacture of isotopically enriched crystalline boron, as a Friedel‐Crafts catalyst in various polymerization, alkylation, and acylation reactions, and in semiconductor doping and etching. Boron subhalides are binary compounds of boron and the halogens, where the atomic ratio of halogen to boron is less than 3. The boron monohalides and boron dihalide radicals have been studied. Diboron tetraflouride, B2F4, diboron tetrachloride, B2Cl4, diboron tetrabromide, B2Br4, and diborontetraiodide, B2I4, are well‐known but thermally unstable compounds.
Chemometrics
Authors: Illman Deborah
Published: August 2004

Chemometrics has been defined as the chemical discipline that uses mathematical and statistical methods to design or select optimal measurement procedures and experiments and to provide maximum chemical information by analyzing chemical data. The definition, historical development, salient methods, and illustrative applications of chemometrics are given. Methods of pattern recognition for exploratory data analysis are discussed, including techniques of scaling, feature weighting, principal components analysis, cluster analysis, classification methods, such as linear learning machine, k‐nearest neighbor, and SIMCA, and modeling methods, such as partial least squares path modeling. Methods for multivariate calibration and resolution are discussed including the generalized standard addition method (GSAM) and the self‐modeling curve resolution approach. Methods to optimize experimental performance, including simplex optimization, are outlined. Illustrative examples of the application of chemometrics in forensic chemistry, environmental chemistry, clinical chemistry, sensor design, and industrial process control are presented.
Color
Authors: Nassau Kurt
Published: August 2004

Two theories of color perception have been dominant. The trichromatic theory relates to blue‐, green‐, and red‐sensitive cones in the retina of the eye. It explains various forms of color blindness and is the basis of the CIE chromaticity diagram using
x, y, Y
. The opponent theory uses the opposites light/dark, red/green, and blue/yellow. It explains a variety of perception phenomena and is the basis of color spaces such as CIE
L
*
a
*
b
*. These apparently incompatible approaches apply to different parts of the color perception process. Modern electronic instruments have greatly simplified the measurement of color.

Fifteen distinct chemical and physical mechanisms explain the various causes of color, all involving the behavior of electrons in matter. Vibrations and simple excitations explain the colors produced by incandescence (flames), gas excitation (vapor lamps), and vibrations and rotations (blue of water). Ligand field effects give the colors of transition‐metal compounds and impurities (turquoise and ruby, respectively). Molecular orbitals give the colors in organic compounds (dyes) and charge‐transfer compounds (blue sapphire). Energy bands lead to the colors of metals (copper), semiconductors (vermilion), doped semiconductors (blue diamond), and color centers (amethyst). Geometrical and physical optics explain colors from dispersive refraction (prism spectrum), scattering (blue sky), interference (soap bubble), and diffraction (opal).
Coordination Compounds
Authors: Archer Ronald D.
Published: August 2004

The chemistry of the metallic elements is predominately coordination chemistry. Coordination compounds often have unique properties relative to both the ligands and the metal ions that make up the compound or complex ion. Coordination compounds are used as catalysts both in nature and industry, as bactericides and fungicides, as polymer components and polymer catalysts, as dyes and pigments, in photographic dyes and processing, in electroplating, in petroleum additives, in drugs and artificial blood, as imaging agents, as components of high temperature superconductors, and in a variety of other uses. The metals and ligands combine to provide a wide range of reactivities in substitution and oxidation‐reduction thermal as well as in photochemical processes. Similarly, the stability of coordination species varies widely with different ligands and metals. Whereas this variation is often simplified to hard and soft acid‐base interactions, gradations exist along with steric selectivity. Coordination compounds have a special nomenclature, exist in a wide variety of coordination geometries, and are intepreted in a variety of theoretical considerations.
Corrosion and Corrosion Control
Authors: Moran Patrick J. , Natishan Paul M.
Published: August 2004

The various types of corrosion, its manifestations, origins, and the fundamental mechanisms responsible are discussed. The importance of electrochemical reactions, both in causing and in controlling corrosion phenomena, is emphasized. The influence of environmental factors and metallurgical variables is reviewed and the predominant corrosion modes for technologically significant metal and alloy systems are discussed. Standard electrode potentials, Pourbaix and Evans diagrams, and a Galvanic series may be found. The various methods of corrosion prevention, such as use of corrosion‐resistant materials, cathodic protection, application of coatings, and addition of inhibitors, are also described.
Cotton
Authors: Bertoniere Noelie R.
Published: August 2004

The history of cotton, the use of which predates recorded history, is reviewed. The various varieties and their origins are given. Modern practices related to cultivation and production, fertilizers, pest and insecticides, harvesting, ginning, and greige processing are presented. Current information on the physical properties of the cotton fiber is given. The use of high volume instrumentation (HVI) for fiber property measurements is included. The morphology of the cotton fiber is discussed. Information on the structure and reactivity of cotton includes its chemical structure, crystal structure, pore structure, and availability of hydroxyl groups. Its chemical reactions that produce value added products are summarized. These products include stretch cottons, durable press fabrics, flame retardant fabrics, waterproof cottons, antibacterial cottons, and temperature adaptable fabrics. Overall economic aspects and health and safety factors are also given.
Cryogenics
Authors: Agrawal Rakesh , Rowles Howard C. , Kinard Glenn E.
Published: August 2004

By accepted international standard, “cryogenics” refers to phenomena and processes occurring at or using temperatures below 120 K. Permanent gases, such as oxygen and helium, can be liquefied at ambient pressure at temperatures of 120 K or below.

Cryogenic technology has contributed greatly to scientific research and is used in a wide range of industrial applications. Cryogenic condensation and distillation processes are widely used to produce high purity oxygen, argon, nitrogen, hydrogen, and helium for the chemical, metal, and electronic industries. These gases and others, such as natural gas, are commonly stored and shipped as cryogenic liquids rather than as pressurized gases. Cryogenic processes are also used to provide low temperatures to refrigerate, freeze, and store other materials, such as food and biological tissue, or to alter the properties of materials, as with superconductivity.

A wide variety of specialized equipment has been developed for cryogenic processes and apparatus, including compressors, expanders, heat exchangers, and distillation columns. Specialized materials have also been developed to insulate cryogenic equipment, transfer lines, storage tanks, and transport vehicles.
Cumene
Authors: Schulz R. C. , Van Opdorp P. J. , Ward D. J.
Published: August 2004

Cumene (isopropyl‐benzene), is the feedstock for the production of phenol and the coproduct acetone in almost all cases, and it is used in minor amounts for other purposes. Physical, chemical, and thermodynamic properties are listed, and pertinent literature sources for the data are given. Methods of manufacture, exclusively by alkylation of benzene with propylene, are discussed, and details of the most prevalent process, which uses a solid phosphoric acid catalyst, are described. Cumene product quality specifications and the typical costs of production are included. Also as part of the economics discussion, the U.S. supply and market price data through April 1992 appear. Several safety and health factors are discussed as are the principal uses of cumene.
Diamond, Natural
Authors: DeVries Robert
Published: August 2004

Naturally occurring diamond is a relatively rare polymorphic form of carbon characterized by a three‐dimensional arrangement of tetrahedrally coordinated carbon atoms. Both natural and synthesized diamond have the highest hardness of all known materials, the highest thermal conductivity at room temperature, a high refractive index and optical dispersion, a low thermal expansion, and a relatively high inertness to chemical attack. This unique combination of properties permits diamond to be foremost in certain applications: as a highly prized gemstone; industrially as an important abrasive material unsurpassed in certain cutting, drilling, sawing, machining, grinding, and polishing operations for many materials; and in electronic and optical applications as a heat sink and window material, respectively. Upstream exploration has sometimes led to the discovery of kimberlite “pipes.” These structures are the principal source of natural diamonds, and there are over 1000 occurrences of them in the world. Only a small number contain a high enough concentration of diamonds to warrant mining. Alluvial diamonds are recovered from streambeds by panning or washing techniques or, more productively, by removal from pockets where the water has concentrated them. High quality gemstones are recovered from ocean deposits off the coast of Africa. A modern method for the separation of crystal from rock uses the emission of light by luminescence of diamond when exposed to x‐rays. The stones are then themselves separated mostly by hand into two main categories, gem and industrial. Besides the single crystals usually implied in a discussion of diamond, the latter also occurs in nature in the form of polycrystalline aggregates. These can be classified into two types, based on origin: carbonado and ballas. Diamond is nominally pure carbon with a
12
C:
13
C ratio of about 99:1. Although other elements are often reported in analyses, only boron, nitrogen, and possibly beryllium are considered to be truly substitutional in the lattice. The classification of diamonds into four types (Ia, Ib, IIa, IIb) is based primarily on the presence or absence of boron and nitrogen and their location in the lattice. Diamond is the hardest material known because of its combination of a three‐dimensional arrangement of tetrahedrally coordinated C–C bonds with a bond distance of 0.154 nm. The Knoop hardness
(K)
is in the range of 68.7–98.1 kN/m
2
(7,000 to 10,000 kgf/mm
2
). Although hard, diamond is also very brittle. The high refractive index (2.42 at 589.3 nm) and dispersion (0.044) are the basis for the brilliance and fire of a properly cut gemstone. The optical transmission out to 10.6 µm for Type IIa diamonds makes possible windows for CO
2
lasers and for devices such as were used in the Venus probe.
Dimensional Analysis
Authors: Chen Wai‐kai
Published: August 2004

Dimensional analysis provides procedures of judicious grouping of variables associated with a physical phenomenon to form dimensionless products of these variables, so that the equation describing the physical phenomenon may be more easily determined experimentally. The concepts of units and dimensions are introduced. The notions of primary and secondary dimensions, dimensional formulas, and the absolute, gravitational, and engineering systems of dimensions are discussed.

Dimensional analysis is based on the premise that any equation that correctly describes a physical phenomenon must be dimensionally homogeneous. To this end, the dimensional matrix is introduced. It is shown that the number of products in a complete set of dimensionless products called the β‐numbers associated with a physical phenomenon is equal to the number of variables that are involved in the phenomenon minus the rank of the associated dimensional matrix. The latter is equal to the maximum number of these variables that will not form a dimensionless product. It states that an equation is dimensionally homogeneous only if it is reducible to a relationship among a complete set of dimensionless products. Finally, a systematic procedure for computing and optimizing a complete set of dimensionless products is described.
Distillation, Azeotropic and Extractive
Authors: Doherty Michael F. , Knapp Jeffrey P.
Published: August 2004

Many industrial processes depend on efficient separation methods for azeotropic or other close‐boiling or low relative volatility mixtures. Whereas ordinary distillation is either uneconomical or impossible in these cases, the addition of specially chosen separating agents can generally facilitate the separation. Four of the five principal techniques employed are discussed: extractive or homogeneous azeotropic distillation, where the liquid separating agent is completely miscible; heterogeneous azeotropic distillation, where the agent, known as the entrainer, forms one or more azeotropes but causes immiscibility; distillation in the presence of ionic salts, which alters the relative volatilities of the components; and pressure‐swing distillation, where a series of columns operate at different pressures. Residue curve maps, material balance lines, and column sequences are given for several commercially important systems. Methods for evaluating total annualized costs are also discussed as are models for determining feasible separating agents.
Glycols, Ethylene Glycol and Oligomers
Authors: Forkner M. W. , Robson J. H. , Snellings W. M.
Published: August 2004

Glycols are diols, compounds containing two hydroxyl groups attached to separate carbon atoms. In an aliphatic chain, ethylene glycol, is the simplest glycol. Diethylene, triethylene, and tetraethylene glycols are oligomers of ethylene glycol. Polyglycols are higher molecular weight adducts of ethylene oxide and are distinguished by intervening ether linkages in the hydrocarbon chain. These polyglycols are commercially important; their properties are significantly affected by molecular weight. They are water soluble, hygroscopic, and undergo reactions common to the lower weight glycols.

The uses for ethylene glycol are numerous. Some of the applications are polyester resins for fiber, PET containers, and film applications; all‐weather automotive antifreeze and coolants, defrosting and deicing aircraft; heat‐transfer solutions for coolants for gas compressors, heating, ventilating, and air‐conditioning systems; water‐based formulations such as adhesives, latex paints, and asphalt emulsions; manufacture of capacitors; and unsaturated polyester resins. The oligomers also have excellent water solubility but are less hygroscopic and have somewhat different solvent properties. The largest commercial use of ethylene glycol is its reaction with dicarboxylic acids to form linear polyesters.

The first commercial application of the Lefort direct ethylene oxidation to ethylene oxide followed by hydrolysis of ethylene oxide remains the main commercial source of ethylene glycol production.

In addition to oligomers ethylene glycol derivative classes include monoethers, diethers, esters, acetals, and ketals as well as numerous other organic and organometallic molecules.
Nonwoven Fabrics, Spunbonded
Authors: Smorada Ronald
Published: August 2004

Spunbonded fabrics are distinguished from other nonwovens by the integration of fiber spinning, web formation, and bonding during manufacture. Spunbonding is an especially efficient method of manufacturing lightweight fabrics, although the sophisticated manufacturing equipment requires significant capital investment. The thermoplastic polymers, polypropylene, polyester, and polyethylene, provide the material base for most of the fabrics produced.

Spinning is accomplished by extruding fibers from either multiple banks or a wide rectilinear spinnerette onto a rapidly moving porous belt. Fibers deposited onto the belt form an unbonded web which then passes through a bonder, typically thermal in nature. This process bonds some of the fibers to neighboring fibers, thus providing integrity to the sheet structure.

Spunbonded fabrics are produced at widths of 3 m or more in order to facilitate productivity. The high speed manufacture of wide‐width, lightweight fabrics of uniform appearance and properties presents many technical problems. The loss of fiber output from just one of the spinnerettes can cause defects which reduce the usable width of the fabrics.

The directionality of the fibers within the fabrics can be controlled during the web‐forming process. This action permits specific physical properties to be engineered into the fabric, although the majority of spunbonded fabrics are, by design, quite isotropic in character.

Spunbonded fabrics are used in many applications, including diaper coverstock, interlinings, wipes, furniture construction, geotextiles, carpet backing, mailing envelopes, and filtration. Spunbonded fabrics are routinely used as components in complex structures that utilize their unique physical properties. The growth of spunbonded fabric sales since the 1960s is indicative of their usefulness.
Coal Conversion Processes, Liquefaction
Authors: Baldwin Robert M.
Published: August 2004

Coal liquefaction involves taking the solid coal to liquid hydrocarbon and oxygenate products. Both direct and indirect routes, the latter being known as the Fischer‐Tropsch process, are known. Direct liquefaction utilizes hydrogenation (hydroliquefaction) or pyrolysis of the coal in a single processing sequence. Indirect liquefaction processes involve the production of synthesis gas, ie, coal gasification, as the first step, followed by catalytic conversion to liquid products.

Liquefaction processes that have moved beyond the laboratory are discussed. Flow diagrams, reactor types and conditions, catalytic composition, conversion efficiency, and product make‐up are given.
Lithium and Lithium Compounds
Authors: Kamienski Conrad W. , McDonald Daniel P. , Stark Marshall W.
Published: August 2004

Lithium, an element of unique physical and chemical properties, is useful in a wide range of applications as the metal, as the lithium ion in inorganic salts, and as the more covalent species in inorganic compounds. The largest uses of lithium compounds are in traditional areas such as the preparation of glass, glass‐ceramics, and enamels; in aluminum cell broth; in the preparation of lithium greases; and as polymerization initiators. Lithium compounds are also employed as psychopharmacological agents and in organic synthesis, catalysis, absorption, air conditioning, photographic processing, and in batteries. Evolving applications include use in fuel cells, electrooptical communications, and as a concrete additive.

The various lithium mineral and brine resources are reviewed along with the processes for lithium extraction and recovery. Manufacturing processes, properties, and applications for lithium metal and lithium compounds are discussed.
Nonlinear Optical Materials
Authors: Dalton Larry R.
Published: August 2004

Nonlinear optical materials are the building blocks of an emerging technology of photonics that uses light to acquire, process, transmit, and store information. These materials perform functions such as modulation, switching, rectification, frequency generation, limiting, and amplification, all of which are typically performed by semiconductors in electronic technology. Nonlinear optical materials and phenomena can be classified as second or third‐order, reflecting the order of electric field interactions involved. Second‐order phenomena are observed only for noncentrosymmetric materials. Such phenomena include electrooptic modulation, spatial light modulation, and second harmonic generation. Electro‐optic modulation may play a critical role in electric‐to‐optical signal transduction and in switching in local area networks. Third‐order phenomena include the dynamic Kerr effect, degenerate four‐wave mixing, third harmonic generation, saturable absorption, reverse saturable absorption, etc. The dynamic Kerr effect can be exploited for all‐optical switching and also for beam focusing, such as in mode‐locking of the Ti:sapphire laser. Reverse saturable absorption can be exploited for sensor protection. Both organic and inorganic materials have been observed to exhibit large optical nonlinearities. Material morphologies ranging from crystalline to polymeric have been considered for nonlinear optical applications; examples of materials are given.
Pigments, Organic
Authors: Jaffe E. E.
Published: August 2004

The article is intended for anyone interested in organic pigments in general or specific pigment classes in particular, with references provided for greater in‐depth review of scientific and theoretical considerations.

The article begins with definition, identification, and categorization of organic pigments, followed by a list of 49 commercial pigments, including methods of their preparation. Also described is the origin of color in organic compounds and the relationship between absorbed light and observed color.

Technical and durability properties are described in some detail, followed by a description of pigment types, including structural formulas of representative pigments, generalized wherever appropriate. For some pigment classes tables are included to identify additional important pigments of a group. In each case, a short description of pigment attributes and shortcoming as well as applications is included. The pigment types range from least expensive, simple pigments, to most sophisticated, complex structures, ranging in properties from poor to excellent.

The description of production and economic aspects are based on governmental statistical data and other information available in the literature, and includes worldwide data with particular emphasis on U.S. consumption, exports, and imports. Finally, methods of pigment testing, standardization, and color measurement are briefly described. The article concludes with a brief discussion of health effects, toxicity of pigments, and their effect on the ecology.
Process Control
Authors: San Giovanni John Paul
Published: August 2004

This article presents the theory and practice of automatic process control and instrumentation, outlining basic concepts of automatic control such as controlled variables, manipulated variables, and control strategies. A functional model of the process control hierarchy is described, as is the role played by modern (digital) control systems equipment. Because reliable process measurements form the foundation for automatic process control, the devices used to measure the basic process variables of flow, level, pressure, and temperature, as well as the practical guidelines for their selections and implementation, are discussed. On‐line process analyzers are also introduced because of their increasing use in process facilities for closed‐loop automatic control. A brief discussion of considerations in the selection and use of control valves is also included.

Conceptual basis and practical aspects associated with both classical and modern (digital) control strategies are discussed. Both continuous and batch processes are considered. The analogue and digital implementations of the classical proportional–integral–derivative controller, cascade control as a technique to improve the overall control performance of a feedback control loop with multiple time constants, and various alternative schemes are presented, including guidelines for selection and design. Ration control is discussed as a form of a multiplicative feedforward control strategy. The use of a selective control strategy to prioritize control actions and to implement overrides and constraint control applications is highlighted. As the use of process integration and the availability of digital‐based control systems grow, more sophisticated control strategies are increasingly employed in process plants. Consequently, important considerations in the design and operation of multivariable control, model‐based predictive control, adaptive control, constraint and optimizing control, and batch sequence control strategies are presented. The economics associated with process instrumentation and control systems is discussed from a benefit–cost standpoint.
Fibers, Regenerated Cellulosics
Authors: Woodings C. R.
Published: August 2004

Fibers manufactured from cellulose are either derivative or regenerated; historically they are designated man‐made fibers and distinguished from fibers based on synthetic organic polymers. A derivative fiber is one formed when a chemical derivative of a natural polymer, eg, cellulose, is prepared, dissolved, and extruded as a continuous filament, and the chemical nature of the derivative is retained after the fiber formation process. A regenerated fiber is one formed when a natural polymer, or its chemical derivative, is dissolved and extruded as a continuous filament, and the chemical nature of the natural polymer is either retained or regenerated after the fiber formation process. The difficulties of making solutions of natural cellulose from which fibers can be spun has led to most fabricated cellulosic fibers being regenerated from more readily soluble derivatives of cellulose. It is the technology of making these fibers that is the subject of this article.

Textiles fibers and filaments composed of regenerated cellulose are called rayons. In Europe the fibers are now generally known as viscose; the term viscose rayon is used whenever confusion between the fiber and the cellulose xanthate solution (also called viscose) is possible. In addition to the viscose process, the cuprammonium rayon and direct dissolution processes are also covered. Fiber properties and environmental and commercial issues are discussed.
Selenium and Selenium Compounds
Authors: Hoffmann J. E. , King M. G.
Published: August 2004

Selenium, the 30th most abundant element, lies between sulfur and tellurium in Group 16 (IVA) of the Periodic Table. There are no ores mined for selenium value. Rather, selenium is recovered throughout the world as a by‐product in the refining of sulfide‐bearing copper minerals. Those processes are discussed.

The chemical and physical properties of selenium are often similar to those of sulfur but are sufficiently different to account for specialized industrial applications. Both inorganic and organic compounds are known. Principal markets for selenium include those as decolorizing agents in glass, photoreceptors for xerography, stable high temperature pigments, free machining additives for steel and brass, and as a nutritional additive to animal and human diets. Selenium deficiency occurs in some parts of the world and diseases relating to this deficiency have been discovered.