VERMILION, a scarlet pigment, which occurs naturally as the crystalline mineral cinnabar. It is the red form of mercuric sulphide, HgS, and is prepared artificially to-day by sublim ing an intimate mixture of mercury and sulphur, or by grinding such a mixture for some hours, digesting it in a solution of caustic potash, and warming at or below C to convert the black mercuric sulphide to the scarlet-red modification ; Chinese ver milion is said to be made by the latter process. Vermilion blackens
in oil on exposure to sunlight and its cost has caused it to be largely superseded by the cheaper and more permanent aniline lakes. See PAINTS, CHEMISTRY OF.