CHEMICAL AND METALLURGICAL

Commercial primary magnesium has a typical purity of 99.8%, which is sufficient for most chemical and metallurgical uses. A typical analysis might be expected to show about 0.003% each of aluminum and copper, 0.04% iron, 0.08% manganese, 0.001% nickel, and 0.005% siHcon. Primary magnesium is available in five grades (Table 3). Considerably higher purity can be obtained by distillation. 

Zinc dust is used in the sherardizing process where work pieces are tumbled with zinc dust in rotating steel dmms which are heated electrically or by gas to 370—420°C (149). The steel parts are uniformly coated with zinc. In the chemical and metallurgical industries, zinc dust is used as a reducing agent, in the manufacture of hydrosulfite compounds for the textile and paper industries, and to enhance the physical properties of plastics and lubricants (2). 

The chemical and metallurgical industries of the world are so varied and extensive that it is impossible to cover all of the processes, emissions, and controls in a single chapter. 

At the end of the nineteenth century, virtually all of the gasoline produced (around 6 million barrels) was used as a solvent by industry, including chemical and metallurgical plants and dry cleaning establishments, and as kerosene for domestic stoves and space heaters. But by 1919, when the United States produced S7.5 million barrels of gasoline, S5 percent was consumed by the internal combustion engine (in automobiles, trucks, tractors, and motorboats). 

A common problem in both chemical and metallurgical practice is that of separating relatively coarse particles, which are called sands, from a slurry of fine particles, which are called slimes. The most common method is to use continuous settling equipment called classifiers. 

Hydrogenation processes usually require standards and materials that may not be warranted in other operations of the petroleum industry. At certain combinations of elevated temperature and hydrogen partial pressure, both chemical and metallurgical changes occur in carbon steel, which in advanced stages can render it unsuitable for safe operation. Alloy steels containing chromium and molybdenum can be used under such conditions. 

Oddy, W. A. (1980), Methods of Chemical and Metallurgical Investigation of Ancient Coinage, Royal Numismatic Society, London. 

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