Metals and their Compounds

Metals and their compounds are a further group of substances with toxic effects on the lung. This is a relatively limited group including the following elements aluminium, arsenic, beryllium, cadmium, chromium, cobalt, copper and nickel. Effects on the lung induced by their compounds are mostly caused solely by the metal part of these substances. Only in a limited number of cases are the effects on the lungs attributed to the entire metal compound. 

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R. Schiele, Manganese in Metals and their Compounds in the Environment, VCH, Weinheim, Germany. 

W. Burkart, in E. Merian, ed., Metals and Their Compounds in the Environment, Occurrence, Mnaljsis, and Biological Kelevance, VCH, New York, 1991, pp. 1275-1287. 

Substances which have an adverse effect on the oxygen balance, particularly ammonia, nitrates The following metalloids and metals and their compounds ... 

Finally, in 1797, the Frenchman L. N. Vauquelin discovered the oxide of a new element in a Siberian mineral, now known as crocoite (PbCr04), and in the following year isolated the metal itself by charcoal reduction. This was subsequently named chromium (Greek xpco ia, chroma, colour) because of the variety of colours found in its compounds. Since their discoveries the metals and their compounds have become vitally important in many industries and, as one of the biologically active transition elements, molybdenum has been the subject of a great deal of attention in recent years, especially in the field of nitrogen fixation (p. 1035). 

Modem processing of tantalum and niobium metals and their compounds is related to the treatment of fluoride compounds. Hence, successful technological improvements, the development of novel methods and the manufacturing of high-grade products depend on the application of technological achievements in the area of fluorine chemistry. 

Although the elements tantalum and niobium were discovered more than 200 years ago in the form of oxides, the true beginning of the chemistry of tantalum and niobium was the discovery and investigation of complex fluorotantalates and fluoroniobates of alkali metals. Application of complex fluoride compounds enabled the separation of tantalum and niobium and in fact initiated the development of the industrial production of the metals and their compounds. 

Thermochemistry and oxidation potentials of the platinum group metals and their compounds. R. N. Goldberg and L. G. HepleT, Chem. Rev., 1968, 68,229-252 (212). 

Actually, the temperature at which the solid becomes mobile also depends on the shape and size of the metal crystallites. For small particles this temperature may become much lower than that indicated by the Tamman or Huttig temperature. Table 3.4 presents Txamnian and THLiftig for some metals and their compounds. 

This brief review has shown that the transition metals and their compounds can play a very useful role in ceramics-directed silicon chemistry. Transition metal complexes find important applications as catalysts as well as stoichiometric reactants, and the metals themselves have found more direct application in the synthesis of silicon-containing ceramics and ceramic composites. 

Many of the metals and their compounds are effective catalysts. 

A study of group 1 (lithium to caesium) and group 2 (beryllium to barium) illustrates the behaviour of metals and their compounds. Conversely, a study of group 7 (chlorine to iodine) illustrates the behaviour of a group of non-metals and their compounds. 

Highly electropositive metals and their compounds are used as initiators, e.g.,Li, BuLi, n-BuMg Br, etc., where Bu represents a butyl group (C4H9). Anionic reactions are very rapid and hence are usually... 

The origin of TSCA is attributed to the CEQ (Council on Environmental Quality) report "Toxic Substances" prepared on April, 1971. This report focused on certain metals and their compounds and... 

Transition metals and their compounds are used as catalysts. Catalysts you may already know are Iron In the Haber process (Industrial production of ammonia) platinum in the Ostwald process (Industrial production of nitric acid) and platinum, rhodium and palladium In catalytic converters. 

The main emphasis was laid, in this initial work, on Haber s catalysts, e.g., osmium and uranium compounds, as well as on a series of iron catalysts. Some other metals and their compounds which we tested are, as we know today, less accessibble to an activation by added substances than iron. Therefore, they showed no improvement or only small positive effects if used in the form of multicomponent catalysts. Finally, the substances which we added to the metal catalysts in this early stage of our work were mostly of the same type as those which had proved to favor the nitride formation, e.g., the flux promoting chlorides, sulfates, and fluorides of the alkali and alkaline earth metals. Again, we know today that just these compounds do not promote, but rather impair the activity of ammonia catalysts. 

A number of metals and their compounds have been found to pose health risks to humans, other animals, and plants. When they occur in air, these metals are sometimes regarded as pollutants. Title III of the 1990 Amendments to the Clean Air Act, for example, lists the following elements and their compounds as "hazardous air pollutants antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, mercury, nickel, and selenium. 

In spite of the failure of alchemy to reach its goals of transmutation, there was a positive gain from the fifteen centuries of alchemical practice. The accumulated knowledge of the particular behavior of metals and their compounds was considerable, and the invention of the art of distillation led to the isolation and characterization of alcohol and the inorganic acids. In its broadest application, distillation became the standard method of analysis by fire. ... 

Mechanism for Deriving Energy. The mechanism by which propulsive energy is derived from propellant systems containing metals and their compounds is somewhat different from that of conventional liquid propellant systems. For hydrazine and nitrogen tetroxide, for example, their combustion leads to the formation of N2, H20, and H2 through a relatively simple series of intermediate species ... 

Because of the toxic and dangerous nature of lead and its compounds, their use is highly undesirable in the propellant formulations. It is in this context that some researchers pursued their work with other metals and their compounds which are either less toxic or non-toxic and a brief account is given in Table 4.11. 

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