CHROMIUM

(Yunanca köken — orijinale bakınız.) A metal discovered by Vauquelin in 17D7. It exists chiefly in two native compounds; the one formerly called red lead of Siberia, which is a chromate of lead j the other, a compound of the oxides of chromium and iron. Chromium is a whitish, brittle, and very infusible metal; sp. gr. S-.'J. When heated with nitre it is converted into chromic acid. Its equivalent number is 28. It forms two compounds with oxygen,— a green oxide, and a red peroxide; the latter being sour, and combining with salefiable bases, is called chromic acid. The oxide consists of 28 chromium +12 oxygen; and chromic acid of 28 chromium+24 oxygen. Chromic acid is of a red colour, and forms a variety of coloured compounds, some of which are much used in the arts; such as the chromate and bichromate of potash, largely manufactured for the use of calico printers, and the chromates of lead, employed as yellow and red dyes and paints. 1 he oxide of chroma is green, and furnishes a valuable colour for porcelain and in enamel. Chromic acid gives colour to the ruby, and the green of the emerald is due to oxide of chroma. [s. 244]