FLUX (

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• LAT

Lat. fluxus, a flowing; this being also the meaning of the

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• ENGLISH

English

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• TERM

term in

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• MEDICINE

medicine, &c.)  , in metallurgy, a substance introduced in the smelting of ores to promote fluidity, and to remove objectionable impurities in the form of a slag . The substances in commonest use are: lime or limestone, to slag off silica and silicates, fluor-spar for lead, calcium and barium sulphates and calcium phosphate, and silica for removing basic substances such as limestone . Other substances are also used, but more commonly in assaying than in metallurgy . Sodium and potassium carbonates are valuable for fluxing off silica; mixed with potassium nitrate sodium carbonate forms a valuable oxidizing fusion mixture; " black flux " is a reducing flux composed of finely divided carbon and potassium carbonate, and formed by deflagrating a mixture of argol with 4 to z its weight of nitre . Borax is very frequently employed; it melts to a clear liquid and dissolves silica and many metallic oxides . Potassium bisulphate is useful in the preliminary treatment of refractory aluminous ores . Litharge and red lead are used in silver and gold assays, acting as solvents for silica and any metallic oxides present .