Metals and metal compounds

Different metals and metal compounds have been in use since the beginning of human civilization. Metals include aluminum, antimony, cobalt, copper, chromium, iron, nickel, manganese, molybdenum, selenium, tin, vanadium, and zinc. The list of toxic metals includes but is not limited to arsenic, beryllium, cadmium, hexavalent chromium, lead, and mercury. Contamination of food, water, and the air by metals, particularly lead and cadmium, has caused global concern. Several studies have shown elevated levels of lead, nickel, chromium, and manganese in children s hair. 

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Workers in the metals treatment industry are exposed to fumes, dusts, and mists containing metals and metal compounds, as well as to various chemicals from sources such as grinding wheels and lubricants. Exposure can be by inhalation, ingestion, or skin contact. Historically, metal toxicology was concerned with overt effects such as abdominal coHc from lead toxicity. Because of the occupational health and safety standards of the 1990s such effects are rare. Subtie, chronic, or long-term effects of metals treatment exposure are under study. An index to safety precautions for various metal treatment processes is available (6). As additional information is gained, standards are adjusted. 

In general, the carbides of metals of Groups 4—6 (IVB—VIB) are prepared by reaction of elementary carbon or hydrocarbons and metals and metal compounds at high temperatures. The process may be carried out ia the presence of a protective gas, under vacuum, or ia the presence of an auxiUary metal (menstmum). 

Table 2. Metals and metal compounds catalysts for SWCNT synthesis (modified from ref. 8).

IARC. 1980. IARC monographs on the evaluation of the carcinogenic risk of chemicals to humans. Vol. 23 Some metals and metallic compounds. Lyons France World Health Organization, International Agency for Research on Cancer, 352-415. 

Unfortunately, most of the elements chosen as promising propellant ingredients are metals and hence solids rather than liquids. The endeavor to incorporate solid-phase metals and metal compounds into liquid propellants has led to a whole new area of propellant technology. Heterogeneous fuels are discussed in detail later. 

Stoeppler, M. 1991. Analytical chemistry of metals and metal compounds, in Metals and their Compounds in the Environment, E. Merian (ed.), VCH, New York, Chap. I.4a., pp. 105-120. 

J.M. Swotinsky, Applied Research on Extruded Rocket Propellants Pleateau-Producing Properties of a Number of Metals and Metal Compounds , PATR 1806 (1951)... 

Chemical contamination does not respect international borders. The contaminants are spread worldwide by air and water. Environmental organic contaminants and inorganic contaminants such as metals and metal compounds, nitrate and nitrite will be present in all foods, though sometimes in quantities below the limit of detection of the analytical methods of today. Moreover, foods as well as raw materials and ingredients for food production are to an increasing extent traded across borders. 

I.T. Brakhnova, Environmental Hazards of Metals Toxicity of Powdered Metals and Metal Compounds, Plenum Press, New York, 1975. 

Another non-equilibrium effect arises when the product composition contains a condensible substance. Solid propellant formulations based upon potassium perchlorate form solid potassium chloride and the acetylenic monopropellants upon decomposition form large quantities of carbon particles, as do very fuel-rich mixture ratios of hydrocarbon propellant systems. More recently metal and metal compounds have been used as fuels and form product oxides which are very high boiling point compounds that condense to varying degrees in the rocket chamber and nozzle. For example, estimates indicate that the normal boiling points of Li20, BeO,... 

Work on potential pollution sources requires a thorough knowledge of the composition of potential pollutants. Maximum parameters should be measured on every industrial effluent that leaves a factory and the fluid that is formed in each landfill. The parameters to be measured include temperature, pH, major dissolved ions, trace elements (mainly metals and metal compounds), organic compounds, and isotopic compositions of hydrogen, oxygen, carbon, sulfur, and nitrogen. To perform such analyses, special laboratories have to be contacted. In certain cases the main product may serve as the label, and in other cases the labels are supplied by accompanying compounds, which in themselves may not be poisonous. 

Action of Water on Metals and Metallic Compounds—Decomposition by Radioactive Substances and Ultra-violet Light- Water ns a Catalyst -Inllueiiee of Desiccation upon the Properties of Substances—Physiological Action. 

The ability of compounds to function as Brpnsted acids or bases is not limited to aqueous solutions, and the reaction of gaseous HC1 and NH3 has already been described. A great many compounds also behave as Brpnsted acids and bases in the molten state. For example, molten NFLtCl and pyridinium chloride (also known as pyridine hydrochloride, C5H5NH+CF) readily undergo reactions that are typical of acids. In some of the early studies on this type of chemical behavior, a large number of reactions of molten NFI4CI with metals and metal compounds were carried out. Typical reactions are illustrated in the following equations ... 

Raspor, B. 1991. Metals and metal compounds in waters. In E. Merian, Ed. Metals and Their Compounds in the Environment Occurrence, Analysis, and Biological Relevance. VCH Publishers, New York, pp. 233-256. 

The contribution of different metals and metal compounds to society through socioeconomic development and improvement in the quality of life needs no emphasis. In fact, over the ages, human civilization has wimessed the role of metals in the civilized world as exemplified in the Stone Age, Copper Age, and Bronze Age. Metals and metal compounds have offered benefits to society and their improper use has caused harmful health effects to mankind. 

The discovery of metals and metal compounds is closely linked to the history of human civilization and advancement of industrial growth and development around the world. How human civilization has passed through centuries and the contribution of different metals and metal compounds for the human development and improvement of quality of life is beyond description and praise. Some of the metals are now known as the metals of antiquity—that is, those metals upon which human civilization took early origin, profusely grew, and is still making advanced growth. The following list shows different metals and metal compounds and the time in history when they were discovered. 

The toxicity, health effects, and related symptoms of poisoning caused by different metals and metal compounds in humans is modulated by many factors. In a large number of instances, poisoning from metal compounds is because of the persistence of the metal dusts and fumes present in the workplace, as well as the properties of each metal, the pattern or route of exposure, the form and nature of the metal, and the quantity or concentration of the metal compound ingested, inhaled, or absorbed into the system. The health status of a worker modulates its toxicity. Toxic metals cause severe poisoning and skin diseases such as melanosis, leukomelanosis, keratosis, nonpitting edema, gangrene, and skin cancer. 

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