bluuebunny/crossref_metadata_2025 huggingface dataset:
Medical Diagnostic Reagents
Authors: Usmani Arthur M.
Published: July 2004

Purified enzymes are widely used as medical diagnostic reagents for the measurement of analytes in urine, other body fluids such as serum and plasma, and even tissue. The enzymes and enzyme‐catalyzed reactions important to these analyses are presented, as are the means for monitoring these reactions. The reactions may be monitored utilizing optical or electrochemical techniques, employing biological indicators, dyes, or other mediators specially designed for the detection system.

Dry chemistry technology employing all necessary reagents, including immobilized enzymes, in hydrogel films formed from suitable polymer is described. The formation of enzyme electrodes for biosensors is discussed. The redox chemistry relating to the diagnostic polymers and other reagents designed for use in this field is presented.
Membrane Technology
Authors: Baker Richard W.
Published: July 2004

Membranes have gained an important place in chemical technology and are being used increasingly in a broad range of applications. The key property that is exploited in every application is the ability of a membrane to control the permeation of a chemical species in contact with it. This article provides a general overview of the entire membrane area. After a review of the historical development of membranes, the principal types of membrane are described briefly. The manufacture of the more important types of membrane and the packaging of membranes in modules to exploit their properties are discussed. The principal membrane applications, including microfiltration, ultrafiltration, reverse osmosis, pervaporation, gas separation, and controlled drug delivery are described. The particular focus is on the use of membranes to solve separation problems. More complete descriptions of some of the important specific applications of membranes are given elsewhere.
Fluorine Compounds, Inorganic, Mercury
Authors: Meshri Dayal T.
Published: July 2004

Mercury(I) fluoride and mercury(II) fluoride are described. Both are commercially available but applications are limited to use of the mercuric fluoride in the fiber optics industry.
Mercury Compounds
Authors: Nowak Milton , Singer William
Published: July 2004

The more widely used inorganic and organic mercury compounds are reviewed. Information as to methods of preparation, properties, and use of these compounds, as well as their current status with regard to U.S. Federal Government regulations, is given. Mercury compounds are used as preservatives and fungicides in coating compositions, as catalysts, as components in semiconductors, and as antiseptics.

The general toxicology of the various classes of mercury compounds is discussed. The methods of dealing with the safety hazards of producing and handling mercurials are also presented, as are the methods of removal of mercury from effluent liquids and gases.
Metal Treatments
Authors: Jackman Laurence A. , Ruiz Carlos N.
Published: July 2004

Operations performed on consolidated metals and alloys are referred to as metal treatments and are usually mechanical or thermal. Mechanical treatments involve changes in shape by forming or machining. Forming entails plastic deformation, which changes the metal microstructure. Plastic deformation can be imparted by hot or cold working. The amount of deformation that can be tolerated is established by workability testing. Primary forming operations convert cast ingots into wrought blooms, billets, bars, or slabs; secondary forming operations produce shapes. Machinability, which indicates the ease or difficulty with which a material can be machined to a given shape, is influenced by metallurgical factors in addition to machining parameters.

In thermal treatments, heat is applied to alter structures and properties, as in annealing or in precipitation hardening, whereby substantial increases in strength can be achieved. Heat treatment of some metals such as steels involves an allotropic transformation. Surface treatments such as shot peening are sometimes used to enhance surface performance. Thermomechanical processing may also be employed. The metals treatment industry is continuously evaluating worker exposure and improving efficiency of treatment processes. Powder metallurgical processes for superalloys are described.
Metal Anodes
Authors: Liederbach Thomas A.
Published: July 2004

Industrial metal anodes can be classified into two groups: the anodes which facilitate a desired reaction, and those from which the product itself is evolved. Anodes can consist of one metal only or be of a conductive structure and carry a catalytic coating. Most technological and commercial advances have occurred in the field of coated metal anodes. Coated metal anodes have replaced the graphite anode in chlorine and sodium chlorate manufacture. Newer applications include cathodic protection systems, high speed electrogalvanizing, and copper foil production. Use of coated metal anodes has led to elimination of some environmental concerns in these industries.

The specific morphology of metallic anode coatings and the condition of the substrate surface have great influence on successful performance. Operating performance is an optimization of anode life and operating voltage. This optimization influences anode structure design and takes into account anode resistance, configuration, and adaptability for recoating.
Methanol
Authors: English Alan , Rovner Jerry , Brown John , Davies Simon
Published: July 2004

English, Alan, and Rovner, Jerry (John Brown); Davies, Simon (Davy Process Technology). The physical and chemical properties of methanol (methyl alcohol), CH
3
OH, are summarized. The evolution of the current low pressure technology based on synthesis gas is presented. The mechanism and functionality of the methanol synthesis catalyst are discussed. Synthesis gas generation processes and feedstocks are described in detail, as are various methanol reactor configurations. The status of current research for future methanol processes, including direct oxidation routes, is summarized. Health and safety aspects of methanol storage and handling are discussed. Worldwide production and consumption data for 1992–1993 are given, together with corresponding end‐use methanol product specification requirements V.
Methyl Chloride
Authors: Holbrook Michael T.
Published: July 2004

Methyl chloride is the simplest chlorinated hydrocarbon and occurs naturally in significant quantities. At ordinary temperatures and pressures it is a colorless gas with a very mild odor and a sweet taste. The principal methods of industrial preparation are methanol hydrochlorination and methane chlorination. Its primary use is in the production of silicone rubbers and as a general methylating agent. A growth rate of 30% is expected for the year 2003. Methyl chloride is regulated by a number of federal and state laws.
Methyl Isobutyl Ketone
Authors: Muthusamy Durai , Fisher Ian
Published: July 2004

Methyl isobutyl ketone (MIBK) (4‐methyl‐2‐pentanone) is an industrially important solvent and chemical intermediate. The properties, manufacturing technologies, uses, and health, safety, and environmental aspects of MIBK are discussed in this article.
Methacrylic Polymers
Authors: Slone Robert V.
Published: July 2004

The commercially relevant and diverse chemistry of methacrylic ester polymers has encouraged their use in a remarkable variety of applications. Within this overview, particular attention is paid to the diversity of properties of methacrylic ester polymers and copolymers, the methods used to produce methacrylic ester polymers with specific properties, and the commercial applications of these materials.
Methylamines
Authors: Turcotte Michael G. , Hayes Kathryn S.
Published: July 2004

Methylamines are derivatives of ammonia with one, two, or all three hydrogen atoms replaced by methyl groups. Amines with alkyl groups of 2‐6 carbons are known as aliphatic amines, and amines with still larger alkyl groups are known as fatty amines. Methylamines are soluble in various organic solvents. All have a strong fishy odor. Methylamines are toxic, colorless gases or compressed liquids. They are highly flammable. Methylamines can be prepared by a variety of methods. Commercial processes involve reaction of methanol with ammonia to form the corresponding mono‐, di‐, and tri‐methylamines. Methylamines are used as intermediates for the manufacture of solvents, agricultural chemicals, water treatment chemicals, pharmaceuticals, surfactants, rubber chemicals, and food/feed additives.
Mica
Authors: Tanner James T.
Published: July 2004

Micas, hydrous aluminum silicate minerals, are characterized by sheet or plant‐like structures and various physical properties. Micas of varying quality are used extensively in the building materials and electrical components industries. They are expected to play a larger role in specialty plastics and as a replacement for asbestos. A detailed description of the mineralogical, chemical, and physical properties of mica is given. Exploration, mining, beneficiation, and processing are also described. Testing methods for and specifications (chemical and physical) of mica products are listed. Mica markets (consumption and exports) are explored. Transportation, marketing, environmental regulations, health and safety factors, and future trends are discussed.
Microbial Polysaccharides
Authors: Cote Gregory L. , Ahlgren Jeffrey A.
Published: July 2004

Cote, Gregory L. and Ahlgren, Jeffrey A. (U.S. Dept. of Agriculture). Microbial polysaccharides are complex carbohydrate polymers produced by a variety of microorganisms. Those of commercial interest are generally produced extracellularly in substantial quantities. Commercial applications can be based on specific structural features or on physical properties. Applications based on physical properties include use as water‐soluble thickeners, gelling agents, and emulsion stabilizers. Applications based on specific structural features include the use of bacterial capsular antigens as vaccines, and the use of polysaccharides as metal complexants. Economically, the most important microbial polysaccharides are xanthan gum, dextran, and gellan. Others, such as pullulan, curdlan, and scleroglucan, are used less in the United States, but significant quantities are used overseas. Other microbial polysaccharides that show promise are bacterial cellulose, emulsan, liposan, levan, and succinoglucan. β‐D‐Glucans and sulfated polysaccharides are of interest as immunomodulators. Vol. 16, pp. 578–611, 372 refs. to November 1993.
Microbial and Viral Filtration
Authors: Aranha‐Creado Hazel , Oshima K.
Published: July 2004

Several physicochemical methods exist to ensure the safety of biological and biopharmaceutical products in manufacture. Whereas physical methods such as heat and radiation may be used, these are often not viable options owing to detrimental effects on product quality. For example, in the case of products that are heat labile or biochemically complex, these methods may result in alteration of the chemistry or function of the product, or random adsorption of key components. Filtration is the separation of particles from a fluid (liquid or gas) by passage of that fluid through a permeable medium. Sterile filtration ensures complete removal of viable organisms. Advances in membrane technology have resulted in the availability of filtrative devices for the removal of viruses in addition to bacteria. Thus membrane filtration is becoming increasingly the method of choice for sterilization of biologicals, especially when the product is heat labile, because the filtration process in inherently nondestructive.

An overview of the general principles of filtration having specific application to bacterial and viral removal is given herein. The emphasis is on ensuring that the sterility and/or safety of biologicals and biopharmaceuticals be maintained.
Microwave Technology
Authors: Osepchuk John
Published: July 2004

Microwaves, in the central portion of the nonionizing spectral region of the electromagnetic spectrum, find use in chemical technology as a power source. Microwaves penetrate macroscopic objects further than other types of nonionizing radiation. Most of the applications of microwave technology are based on heating effects related to the dielectric properties of the various media. Consumer products are limited to microwave ovens which are used for cooking, reheating, and thawing foods.

The frequency allocations for microwave technology and the basic principles for materials processing are described as are the components of microwave instrumentation, the requirements for radio‐frequency interference shielding, and the limitations in frequency exploitation. Applications related to food processing and various forms of food packaging are discussed. Microwave power sources also find use in ceramics processing, medicine and other biological applications, and have potential in such fields as thin‐film deposition and waste treatment.
Milk and Milk Products
Authors: Hall Carl W.
Published: July 2004

Hall, Carl W. (Engineering Information Services). Milk from cows is a significant food source throughout the world. Milk provides food components to meet important nutritional needs of the human body. Vitamins, minerals, sugar, fat, and protein are contained in milk. The amount of these components in milk varies with the breed of animal, the particular animal, and with other species that produce milk. As a human food, care must be taken in the production and processing of milk and milk products to maintain quality. Contamination must be avoided. Appropriate temperature control must be provided to hold raw milk, process milk into beverage, process milk into its many products, and deliver quality products to the consumer. Changing consumer habits influence the kind and amount of products manufactured. Appropriate quality determinations and controls must be provided throughout the process to assure that safe, nutritious products are delivered to the consumer on an economical basis. Vol. 16, pp. 700–746, 53 refs. to June 1993.
Mineral Nutrients
Authors: Enig Mary G.
Published: July 2004

The essential mineral nutrients are classified into two groups: the principal elements calcium, phosphorus, sulfur, potassium, sodium, chlorine, and magnesium; and the trace and ultratrace elements iron, fluorine, zinc, silicon, copper, boron, selenium, iodine, manganese, molybdenum, chromium, cobalt, tin, vanadium, and nickel. These minerals perform a wide variety of functions serving as components of bones and teeth (calcium, phosphorus, fluorine); as components of cellular membranes (phosphorus); as high energy compounds (phosphorus); as components of proteins and amino acids (sulfur); in maintaining the appropriate pH and water volume of the organism (sodium, potassium, chlorine); in regulating metabolic rate (iodine); as components of (or cofactors for) enzymes (copper, zinc, selenium, molybdenum, manganese, iron, magnesium, calcium); in formation of hemoglobin (iron, cobalt, copper); in prevention of dental caries (fluorine); and in maintaining the appropriate level of muscle and nerve excitability (sodium, potassium, calcium, magnesium). Information is included on body content, daily requirement, effects of excess, deficiency or faulty utilization, modes of absorption and excretion, metabolic functions and modes of action, food sources, and toxicities.
Minerals Recovery and Processing
Authors: Nagaraj D. R.
Published: July 2004

Minerals recovery from the earth's crust and the subsequent processing of economic mineral deposits, ie, ores, constitutes a wide variety of steps. Taken together these represent one of the world's largest industries. Liberation of the value minerals from the ore matrix is a significant undertaking as is the disposal of the gangue materials or tailings once processing is complete. Materials handling is a significant problem in minerals processing as is process or plant control. Massive quantities of material, ie, ores, solvents, additives, and gangue, must be handled for separation procedures. Most mined ore undergoes size reduction, ie, grinding or crushing, and size separation and classification prior to minerals concentration.

Minerals separation or concentration methods may include ore sorting, gravity concentration, magnetic or electrostatic separations, flotation, or combinations of these methods, depending on the ore, the mineral, and economic considerations. These methods are described as are the various solid–liquid separation, ie, dewatering, procedures, which may include thickening, filtration, centrifugal dewatering, or thermal drying. The methods of choice for several minerals are given as examples.
Mixing and Blending
Authors: Hemrajani Ramesh R.
Published: July 2004

Fluid mixing is a unit operation carried out to homogenize fluids in terms of concentrations, physical properties, and temperature, and create dispersions of mutually insoluble phases. It is frequently encountered in process industries such as petroleum, chemical, food, pharmaceutical, paper, and mining. Applications range from 0.01 m
3
reactors to 20,000 m
3
product storage tanks and continuous in‐line mixers. The fundamental mechanism of mixing involves physical movement of material between various parts of the whole mass by transmitting mechanical energy. Adequate mixing is a prerequisite for the success of chemical processes for minimizing investment and operating costs. In addition, chemical reactions with mass‐transfer limitation can be enhanced to provide high yields. Good mixing, therefore, plays a significant role in the profitability of the process industry.

Mixing systems are broadly divided into single‐phase systems involving miscible liquids; and multiphase systems such as solid–liquid, mutually insoluble liquids, and gas–liquid. Fundamental mixing concepts and suitable mixer types, design, and scale‐up issues for these mixing classes are discussed. The mixing equipment described includes agitated tanks, jets, static mixers, unique designs for powders and pastes, and devices for transferring heat. Blending of low and high viscosity liquids and suspension of sinking and floating solids are covered in more detail.
Molecular Sieves
Authors: Kühl Günter H. , Kresge Charles T.
Published: July 2004

Molecular sieves are inorganic materials that possess uniform pores with diameters in either the micro‐ or meso‐size range. Heterogeneous catalysis and adsorption processes make extensive use of molecular sieves. The utility of these materials is manifested in their microstructures, which allow access to large internal surfaces and cavities that enhance catalytic and adsorptive capacity.

The most technologically important molecular sieves are zeolites, which are high capacity, selective adsorbents capable of separating molecules based on the size and shape of the molecule relative to the size and geometry of the main apertures of the structures. They adsorb molecules with a selectivity that is not found in other solid adsorbents. Structure, manufacture, uses, properties, health and safety factors, and economic aspects are discussed.
Molecular Recognition
Authors: Weber Edwin
Published: July 2004

Molecular recognition is a central point. It may be said that without molecular recognition, there would be no life on this world. Vital biochemical processes such as enzyme action, molecular transport, genetic information, processing and protein assembly all involve molecular recognition as an essential action. Understanding of its principles is still a problem although a first elucidation of the rules that govern molecular recognition dates back to the late nineteenth century. The “lock‐and‐key” principle (1894) proposed that enzyme and substrate can be compared to lock and key getting selectivity between molecules involved. Earlier it was recognized that molecules do not act if they do not bind, thus introducing the concept of receptor. Finally binding or fixation requires interaction, affinity between the partners, that may be related to the idea of coordination of Werner.

According to these basic concepts, molecular recognition implies complementary lock‐and‐key type fit between molecules. The lock is the molecular receptor and the key being the substrate that is recognized and selected to give a defined receptor–substrate complex, a coordination compound or a supermolecule. Hence molecular recognition is one of the three main pillars, fixation, coordination, and recognition, that lay foundation of what is now called supramolecular chemistry.
Molybdenum Compounds
Authors: Stiefel Edward I.
Published: July 2004

Molybdenum, found naturally as molybdenite, is converted through MoO3to compounds in a wide range of oxidation states, coordination numbers, and states of aggregation. The diverse chemistry of molybdenum is manifest in a wide array of uses in biological and industrial systems. Molybdenum, an essential component of many enzymes, plays a primary role in nitrogen fixation and nitrate reduction in bacteria and plants, and sulfite and xanthine oxidation for microorganisms, plants, and animals. Industrially, molybdenum compounds are important in lubrication, where the disulfide and oil‐soluble molybdenum sulfur complexes serve as antifriction and antiwear agents; in hydrodesulfurization and hydrotreating of petroleum; ammoxidation and other catalytic processes; in anticorrosion formulations; as flame and smoke retardants; and in a variety of coatings and pigments. Biomedically, molybdenum is used in nuclear medicine and is under study in a number or therapeutic procedures. The trioxide, several molybdates, and the disulfide are available as bulk chemicals.
Monobactams
Authors: Lindner Klaus R. , Bonner Daniel P. , Koster William H.
Published: July 2004

β‐Lactam antibiotics are one of the best established classes of antimicrobial agents for the treatment of infectious diseases. By screening strains of bacteria that were specifically responsive to β‐lactam antibiotics, monocyclic β‐lactams, ie, monobactams, varying in substitution at the C‐3 position, were identified. The naturally occurring monobactams include SQ 26,180 (), SQ 26,445 (C12H20N4O9S), sulfazecin (C12H20N4O9S), and isosulfazecin (C12H20N4O9S). More recently, the 4β‐methyl analogue of SQ 26,445/sulfazecin was isolated using a differential antibacterial assay. Initial syntheses employed the sulfonation of an N‐1 unsubstituted azetidinone as the key step. The natural product SQ, 26,180 as well as other methoxylated monobactams were synthesized. Subsequently, many more C‐3 side‐chain analogues were prepared. A second, distinct chiral synthesis of monobactams was developed from β‐hydroxy amino acids. The methodology was also applied to the synthesis of 4α‐ and 4β‐methyl monobactams. The monobactams, like penicillins and cephalosporins, interfere with the synthesis of bacterial cell walls. B‐Lactam antibiotics bind to a series of penicillin‐binding proteins (PBPs) on the cytoplasmic membrane and their antibacterial effect is believed to result from inhibition of a subset of these PBPs known as peptidoglycan transpeptidases. Although naturally occurring monobactams have exhibited poor antibacterial activity, alteration of the C‐3 amide side chain has led to many potent new compounds. Aztreonam is a totally synthetic compound that exhibits potent and specific activity against a wide range of both β‐lactamase‐producing and nonproducing aerobic gram‐negative bacteria, includingPseudomonas aeruginosa, but displays minimal inhibition against anaerobic and gram‐positive aerobic bacteria, eg, staphylococci and streptococci. Two monobactams were in clinical use as of 1990. Aztreonam, manufactured by Bristol‐Myers Squibb, has the worldwide trademark of Azactam. Carumonam, manufactured by Takeda in Japan, has the trademark Amasulin.
Thin Films, Monomolecular Layers
Authors: Ulman Abraham
Published: July 2004

Monomolecular layers, the thinnest of thin films, can be prepared by Langmuir‐Blodgett techniques or can result from self‐assembly of monolayers. The former generally takes place at a solvent–air interface. Self‐assembled monolayers generally form by adsorption of a surfactant‐like molecule on a solid substrate placed in a solution. Layers generally consist of large surfactant molecules, having both hydrophilic and hydrophobic sections. The design, preparation, and properties of these films are discussed. The various types of multilayer films are presented, as are the types of substrates employed. Whereas commercial production of these films has yet to be realized, the potential for monomolecular layers in sensors, electrooptics, and semiconductors is large.
Naphthenic Acids
Authors: Brient James A. , Wessner Peter J. , Doyle Mary Nn
Published: July 2004

Naphthenic acids are mixtures of naturally occurring cycloaliphatic carboxylic acids recovered from petroleum distillates. The acids are present in varying amounts in crude oil and are typically recovered by caustic extraction of petroleum distillates boiling in the 200–370°C range. Commercial naphthenic acids are sold in various grades of purity. This article is a compilation of information on their composition, occurrence, manufacture, analysis, and expanding uses and was collected from a review of the literature through mid‐1993. Particular attention is paid to recent analytical methods that elucidate the structure of the various components of this complex mixture. In addition to the traditional wood‐treating and paint drier applications for the metal naphthenate soaps, new derivatives such as naphthenate esters and amides with uses as lubricants, surfactants, and corrosion inhibitors are also emphasized. An extensive supplementary bibliography is included for more detailed discussion of the referenced material.
Naphthalene Derivatives
Authors: Talukder Mannan , Kates Curtis R.
Published: July 2004

Naphthalene derivatives are of diverse importance as intermediates for agricultural, construction, pharmaceutical, photographic, rubber, tanning, and textile chemicals. Production figures, economics, and processes are discussed on most commercially important compounds. Not many processes for manufacturing naphthalene derivatives have changed in recent years, though there are a few changes in the equipment design, the material of construction and in refining techniques to meet environmental regulations. Use of high purity petroleum‐derived naphthalene has, in some cases, resulted in better purity of the derivatives and elimination of expensive prepurification steps.

Phenyl‐1,4‐dihydroxy‐2‐naphthoate has an important application in photographic materials in the United States, Europe, and Japan. Much attention has been focused on the manufacture of 2,6‐naphthalenedicarboxylic acid, a potential monomer in the production of polyester fibers and plastics with superior properties. Most naphthalene derivatives are intermediates and are manufactured for captive use, so that true production figures are difficult to obtain. Vol. 16, pp. 979–1017, 143 refs. to June 1994.
Neuroregulators
Authors: Briggs Clark A. , Holladay Mark W. , Kerwin James F. , Sullivan James P. , Williams Michael
Published: July 2004

Neuroregulators represent a diverse group of compounds that include both neurotransmitters and neuromodulators. Receptors for neuroregulators on both the cell surface and within the cell represent the molecular targets of the majority of drugs in clinical use. In order to classify an endogenous agent as a neurotransmitter, it must possess a number of general characteristics, which are described. Neurotransmitter receptors are grouped according to sequence homology and structures are given. In many cases human receptors have been cloned.
Nickel Compounds
Authors: Antonsen D. H.
Published: July 2004

Nickel compounds can be divided into the classic inorganic salts and a wide variety of organonickel compounds. The various compounds find use as plating salts, catalysts, in specialty ceramics and chemicals, as pigments, and in nickel metal refining. Commercially the most important are the inorganic nickel(II) compounds and nickel carbonyl, a highly toxic nickel(0) species.

Nickel salts form a wide variety of complexes with nitrogen, phosphorus, and sulfur, as well as with oxygen and carbon π‐systems. Properties, manufacture, and uses of nickel compounds and complexes are discussed.
Niobium and Niobium Compounds
Authors: Schlewitz James H.
Published: July 2004

Niobium, also known as columbium, is used primarily as an alloy addition to steels. Ferroniobium and nickel‐niobium are the most frequently used alloys. Niobium is also vital to the formation of superalloys, and its compounds find use in nuclear fuel rods, optical glass, as ferroelectrics, semiconductors, and in superconducting material. Of primary interest is the stability of niobium metal and its alloys to corrosion. The occurrence, extraction, refining, and metallurgy of niobium is described. The analytical procedures for determination of niobium and its impurities are discussed. The primary niobium compounds, which range from the refractory borides and carbides through the ferroelectric salts of niobic acid, are presented.
Nitrobenzene and Nitrotoluenes
Authors: Adkins Rick L.
Published: July 2004

Nitrobenzene is a pale yellow to yellowish brown liquid with a boiling point of 207–212°C, depending on its purity. It is a very toxic substance with a maximum allowable concentration (PEL) of 1 ppm. In 1992, 612,350 metric tons of nitrobenzene were produced with a bulk price of $0.73/kg. The commercial production of nitrobenzene involves the direct nitration of benzene using a mixture of nitric and sulfuric acids, with typical yields of 96–99%. The main derivatives of nitrobenzene areortho‐,meta‐, andpara‐nitrochlorobenzene. These are toxic, with a PEL of 0.1 ppm forp‐nitrochlorobenzene.

Nitrotoluene exists as three isomers:o‐,m‐, andp‐nitrotoluene. Theo‐ andm‐nitrotoluenes are clear yellow liquids at 25°C, whereasp‐nitrotoluene is a crystalline solid (mp 53.5°C). The nitrotoluenes are fairly toxic, with a PEL of 2 ppm. In 1992, 26,000 metric tons of mononitrotoluene were produced, with the bulk prices foro‐,m‐, andp‐nitrotoluene being $1.15/kg, $2.54/kg, and $3.64/kg, respectively. The commercial processes for mononitrotoluene and nitrobenzene are similar.
Nitration
Authors: Albright Lyle F.
Published: July 2004

Organic compounds are nitrated by both ionic and free‐radical reactions. Ionic nitrations are employed extensively with aromatics, compounds containing hydroxy groups (such as alcohols, glycerol, and cellulose), and amines. Nitronium ions (

) and sometimes nitrosonium ions (NO
+
) attack the above compounds to start the nitration reactions. Nitronium ions are present in most nitrating agents employed, including mixtures of HNO
3
and H
2
SO
4
; mixtures of N
2
O
4
and H
2
SO
4
; HNO
3
; and N
2
O
5
. The chemistry and physical steps during nitrations that involve two liquid phases are discussed. Key features of several important commercial nitrations are described, which in some cases exhibit extremely rapid rates of nitration. Considerable effort has been made to develop commercial processes with improved safety of operation, reduced environmental problems, lesser energy demands, lower operating costs, and increased yields of nitrated products. Certain nitrated products can only be produced using N
2
O
5
as a nitrating agent. Some N
2
O
5
processes likely will be commercialized in the near future for the production of high explosives and nitramines. Paraffins and cycloparaffins react with HNO
3
or NO
2
via free‐radical steps to form nitroparaffins. The chemistry and processes are discussed. Vol. 17, pp. 68–80, 39 refs. to June 1993.
Nitro Alcohols
Authors: Bollmeier Allen F.
Published: July 2004

Nitro alcohols are obtained from nitroparaffins by reaction with aldehydes in the presence of an alkaline catalyst. Only 2‐nitro‐1‐butanol, 2‐ethyl‐2‐nitro‐1,3‐propanediol, 2‐methyl‐2‐nitro‐1‐propanol, 2‐methyl‐2‐nitro‐1,3‐propanediol, and 2‐hydroxymethyl‐2‐nitro‐1,3‐propanediol, the five nitro alcohols produced with formaldehyde, are manufactured in commercial quantities. All these nitro alcohols except nitrobutanol are crystalline solids when pure, are highly soluble in water, and are only moderately toxic by ingestion.

The principal use of the nitro alcohols is as intermediates for the synthesis of amino alcohols by hydrogenation. The nitro alcohols also are a convenient starting material for the synthesis of diamines by a two‐step process involving the formation of a nitro amine by reaction of the hydroxyl group with a primary amine followed by hydrogenation.

2‐Methyl‐2‐nitro‐1‐propanol finds commercial use to promote adhesion of rubber to tire cord in radial tires. It also can serve as a source of formaldehyde in polymer cross‐linking. 2‐Hydroxymethyl‐2‐nitro‐1,3‐propanediol is a registered biocide useful for control of bacteria in such end uses as metalworking fluids and cooling tower water. This compound also finds acceptance in chemical toilets as an odor control agent.
Nitroparaffins
Authors: Bollmeier Allen F.
Published: July 2004

Four nitroparaffins are commercially available. These four, nitromethane, nitroethane, 1‐nitropropane, and 2‐nitropropane, are medium‐boiling liquids which are excellent solvents for a wide variety organic compounds and polymers. Some physical properties of these nitroparaffins and a few higher mononitroparaffins and polynitro compounds are presented. The nitroparaffins can undergo a number of reactions which give them utility for synthesis of other compounds of commercial importance. These reactions are discussed. Of particular importance is their ability to form nitronate salts with alkalis. This reaction is the first step for the halogenation reaction, eg, for the synthesis of the fumigant chloropicrin, or the condensation with carbonyl compounds for the synthesis of nitro alcohols.

Production of the four commercial nitroparaffins is by vapor‐phase nitration of propane with nitric acid. Some 41,000 t of mixed nitroparaffins can be produced annually. All the nitroparaffins are flammable liquids. Their principal hazard is by inhalation. Special attention is required for handling nitromethane because it can be detonated under certain circumstances. The bulk of nitroparaffin production is used for synthesis of other chemical products. Nitromethane is useful as a fuel in drag racing and model airplanes, however, and nitroethane and 1‐nitropropane see use as solvent in coatings.
Nitric Acid
Authors: Clarke Stephen I. , Mazzafro William J.
Published: July 2004

Nitric acid is a strong acid, a powerful oxidizing compound, and a nitrating agent. These properties make it an important basic chemical compound that is used in the production of many important chemicals such as fertilizers, polyurethanes, organic chemical intermediates, pharmaceuticals, synthetic fibers, dyes, insecticides, fungicides, and explosives. Nitric acid is produced through the oxidation of ammonia to nitrogen oxides, which are then absorbed by water to produce nitric acid. Weak nitric acid processes produce nitric acid in the concentration range of 50–65 wt %. The two main types of weak acid process are the monopressure process and the dual‐pressure process. The monopressure process operates at either moderate (0.3–0.6 MPa) or high pressure (0.7–1.2 MPa). The dual‐pressure process performs the conversion of ammonia at atmospheric or moderate pressures (0.3–0.6 MPa) and the absorption of nitrogen oxides at high pressure (1.1–1.5 MPa). Nitrogen oxides in the tail gas leaving the process are reduced to below environmental regulatory limits by either extended absorption or catalytic abatement. Strong nitric acid of 98–99 wt % is produced by either extractive distillation or direct strong nitric acid process. The extractive distillation process uses either magnesium nitrate or sulfuric acid as a dehydrating agent to surpass the maximum boiling azeotrope of nitric acid. The direct strong nitric acid process is similar to the weak nitric acid process, but has additional processing steps that bypass the azeotrope to produce strong nitric acid. Information on the chemical and physical properties, manufacturing processes, materials of construction, uses, safety and health, analytical methods, and process licensors of nitric acid is included.
Nitrile Rubber
Authors: Mackey Donald , Jorgensen August H.
Published: July 2004

Nitrile rubbers are copolymers of 1,3‐butadiene and acrylonitrile that have been produced by emulsion polymerization for about 50 years. They carry the ASTM designation NBR. A wide variety of products are available from a number of worldwide suppliers. The primary uses of NBR are in seals, O‐rings, hose, and gaskets, where resistance to hydrocarbon fluids like gasoline and oil is required. A second important use is in the modification of plastic materials to provide impact resistance and flexibility. This article covers the properties and uses of NBR and its hydrogenated derivative HNBR. Manufacturing processes, world usage and capacity, and toxicological considerations are also described.
Nitrides
Authors: Markel Eric J. , Leaphart M. E.
Published: July 2004

Nitrides may be classified as being ionic or salt‐like, metallic, nonmetallic or diamond‐like, or volatile. Additionally, sulfur and phosphorus form polymeric nitride species. Whereas many nitrides exist, only a few are produced commercially. Transition‐metal binary nitrides, made on a small scale, are used for high strength and hardness primarily as refractory coatings. Boron, aluminum, and silicon nitrides are produced on much larger scales and find use as refractories, ablative materials, abrasives, and coatings. Lithium nitride finds application in batteries and catalysts. Gallium and indium nitrides are used in such optoelectronic devices as light‐emitting diodes. The properties of transition‐metal metallic nitrides and the diamond‐like nonmetallic nitrides are described. The manufacture and processing of nitride coatings by case hardening is presented as well as the processing of the structurally important silicon nitride.
Antibacterial Agents, Nitrofurans
Authors: Schwan Thomas J. , Ebetino Frank H.
Published: July 2004

The nitrofurans encompass a class of synthetic antibacterials characterized by the 5‐nitro‐2‐furanyl group. Nitrofurans include furium, C9H7N3O4S; furazolidone,\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{C}}{_{14}}{\rm{H}} _{12}{\rm{N}}{_{6}}{\rm{O}}{_{6}}{\rm{{\cdot{}}}}{\rm{HCl}}}$\end{document};Z‐furan, C7H6N2O4; furylfuramide, C11H8N2O5; nitrovin,\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{\rm{C}}{_{14}}{\rm{H}} _{12}{\rm{N}}{_{6}}{\rm{O}}{_{6}}{\rm{{\cdot{}}}}{\rm{HCl}}}$\end{document}; furalazine C9H7N5O3; acetylfuratrizine, C11H9N5O4; panfuran‐S, C11H11N5O5; nifuroxime, C5H4N2O4; nitrofurazone, C6H6N4O4; nifuraldezone, C7H6N4O5; nihydrazone, C7H7N3O4; nitrofurantoin, C8H6N4O5; nifuratel, C10H11N3O5S; nitrofurathiazide, C13H12N4O6S; nifurtoinol, C9H8N4O6; and nifurprinol, C12H10N2O4. Several nitrofurans have been marketed in the human and veterinary areas because of their broad spectrum of activity and relatively mild toxicity. Nitrofurans are generally stable, water‐insoluble crystalline solids, which decompose (darken) upon prolonged exposure to light or alkali. Nitrofurantoin is bactericidal at the concentrations achieved in the urinary tract and highly effective against the corresponding pathogens. Since its introduction for use in uncomplicated urinary tract infections, essentially no resistance development has occurred, unlike nearly all other antimicrobials. Nitrogurazone, furazolidone, and nitrofurantoin have been used therapeutically for over 30 yr with no reports of human neoplasia. Most commercial nitrofurans are derived from 5‐nitro‐2‐furancarboxaldehyde or the corresponding diacetate.
N‐Nitrosamines
Authors: Wishnok John S.
Published: July 2004

N‐Nitrosodialkylamines (nitrosamines) are a large group of substances containing the NNO group and various substituents on the amine nitrogen. They can be synthesized by reaction of the corresponding amines with nitrosating agents such as acidic nitrite, N2O3, N2O4, or inorganic nitrosyl compounds. They can be analyzed by gas or liquid chromatography with detection generally based on measurement of nitric oxide that is released from the nitrosamines by pyrolysis, photolysis, or acid hydrolysis. Many of the nitrosamines are agents which damage the liver in animals and humans. Most nitrosamines are known animal carcinogens, and some are suspected human carcinogens. Nitrosamines are metabolized by several enzyme systems, the most important being the cytochrome P450 family. Metabolic conversion to active electrophiles that react with DNA appears to be the initiating event in nitrosamine carcinogenesis. Humans may be exposed to nitrosamines by several routes including diet, commercial or industrial preparations such as cutting fluids, cosmetics, or sunscreens, tobacco products, and synthesis inside the body. Nitrosamines have not been unequivocally shown to be human carcinogens, but evidence relating oral cancer to the use of smokeless tobacco is increasingly persuasive.
Nomenclature In the Petroleum Industry
Authors: Barker Colin
Published: July 2004

Activities in the petroleum industry range from exploration, to oil and gas recovery or production, refining, distribution, and marketing. The nomenclature used has been derived from the disciplines of geology, petroleum engineering, and chemistry. This, combined with the complex nature of oil and many refined products, makes for a terminology that is often not systematic and has many poorly defined terms. An outline of the more widely used terms from exploration, production, and refining is included.
Nondestructive Evaluation
Authors: Bray Donald E.
Published: July 2004

The technology of nondestructive evaluation (NDE) includes all nondamaging or nonintrusive methods for determining material identity; for evaluating material properties, composition, structure, or serviceability; and for detecting discontinuities and defects in materials. Nondestructive tests commonly are used for quality control, process control, and for reliability assurance of materials, protective coatings, components, welds, assemblies, structures, and operating systems. The use of these tests helps prevent premature failure of materials during processing, manufacturing, or assembly, and during service under anticipated operating stresses and environments. Nondestructive evaluation provides an essential service toward achieving the goal of optimum plant and system operation.

An overview of NDE methods and applications that apply to most inspection demands that can arise in the chemical industry is presented. Candidates for inspection with NDE range from massive aircraft and pressure vessels to minute fibers used in the construction of high strength composites and fine arts objects. Techniques applicable to such a wide range of items may be classified as external energy tests, where the signal or probing medium is generated externally to the system being evaluated, or passive energy tests, where the signal comes from the system itself. Probe sources range from the ultrasonic and microwave through γ‐ and x‐rays. Surface investigation, leak detection, flaw sizing, imaging of material systems, and routine inspections are all carried out using NDE.
Nonlinear Optical Materials
Authors: Dalton Larry R. , Bale Denise H.
Published: July 2004

Nonlinear optical materials are the building blocks of the emerging technologies of optoelectronics and photonics (photonics 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 typically observed only for noncentrosymmetric materials. Such phenomena include electrooptic modulation, spatial light modulation, and second harmonic generation. Electrooptic modulation may play a critical role in electric‐to‐optical signal transduction and in switching in local area networks and can be used for specialized applications as diverse as phased array radar and optical gyroscopes. 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 relatively large optical nonlinearities. Material morphologies ranging from crystalline to polymeric to photonic bandgap have been considered for nonlinear optical applications; examples of materials are given.
Ceramics, Nonlinear Optical and Electrooptic Ceramics
Authors: Phillips Mark L. F.
Published: July 2004

Nonlinear optical (NLO) and electrooptic (EO) processes are events that take place in transparent materials where refractive indexes can vary with electric field intensity. The field elicits a polarization response in which terms dependent on second and higher orders of the field intensity become significant contributions to the overall polarization response. As light propagates through a transparent solid, liquid, or gas, it encounters the electric fields associated with the valence electrons, polarizing them and creating oscillating electric dipoles. These oscillators in turn act as antennas to broadcast or propagate the electric field through the medium.

NLO materials possess a high degree of optical nonlinearity, physical durability and chemical inertness, and high threshold to optical damage. In addition, it must be possible to process the materials into the form required by the intended application.

Optically nonlinear ceramics all contain highly polarizable bonds. In the case of oxide ceramics, such polarizable bonds are often found between oxygen and early transition metals, eg, BaTiO
3
, SrNb
2
O
6
. Nonoxide NLO ceramics include Si and compound semiconductors having the silicon structure, eg, GaAs, InP, and InSb, as well as ferrelectrics such as SbSI. All‐optical wavemixing applications generally require single crystals.

Electrooptic (EO) materials are optical media in which birefringence can be readily induced or altered by an externally applied electric field. As with NLO ceramics, good EO materials tend to be ferroelectrics. EO materials are generally used as either bulk optical elements or guided wave devices.
Odor Modification
Authors: Berry Yvette
Published: July 2004

Odor modification is defined by the impact of one odorous substance upon another, thereby altering the perception of the primary odor in some manner. This phenomenon can occur in different ways. The masking of an odor results when the original odor is compounded with an additional odor, and an overall increased perception in intensity is realized. Counteraction occurs when the perception of the combination of the two odorants results in an overall decreased perception in intensity. Both of these relationships are reviewed in detail. Initially, this article examines the basic mechanism of olfaction, classification of odors, and how odor counteraction is evaluated. Finally, it touches upon the use of odors to modify not only the perception of other odors but human behavior as well.