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refining,any of various processes for separating impurities from crude or semifinished materials. It includes the finer processes of metallurgy, the fractional distillation of petroleum into its commercial products, and the purifying of cane, beet, and maple sugar and many other substances. The nature of the refining process depends on such factors as the type of material involved, the value of the end product, and the degree of purity necessary. The purification of a metal is based upon physical or chemical differences between the metal and its accompanying impurities, including density, melting point, magnetic properties, and reaction to certain chemicals. It may be accomplished by a continuation of a process used in separating the metal from its ore. Electrolysiselectrolysis
, passage of an electric current through a conducting solution or molten salt that is decomposed in the process. The Electrolytic Process
The electrolytic process requires that an electrolyte, an ionized solution or molten metallic salt, complete an
..... Click the link for more information. is much used in the refining of various metals (e.g., copper); the open hearth process (see steelsteel,
alloy of iron, carbon, and small proportions of other elements. Iron contains impurities in the form of silicon, phosphorus, sulfur, and manganese; steelmaking involves the removal of these impurities, known as slag, and the addition of desirable alloying elements.
..... Click the link for more information. ) and the basic oxygen processbasic oxygen process,
method of producing steel from a charge consisting mostly of pig iron. The charge is placed in a furnace similar to the one used in the Bessemer process of steelmaking except that pure oxygen instead of air is blown into the charge to oxidize the impurities
..... Click the link for more information. are used in the refining of iron; the amalgamation processamalgamation process
, in particular, a method to extract gold and silver from ores. The ore is crushed and treated with mercury, in which the metal dissolves. The amalgam is heated and the mercury evaporates, leaving pure gold or silver.
..... Click the link for more information. and the cyanide processcyanide process
method for extracting gold from its ore. The ore is first finely ground and may be concentrated by flotation; if it contains certain impurities, it may be roasted.
..... Click the link for more information. are chemical means of metal refining.