CORROSIVE SUBLIMATE, Mercuric Chloride, Perchloride of Mercury (HgCl2), a white solid obtained by the action of chlorine on mercury or calomel, by the addition of hydrochloric acid to a hot, strong solution of mercurous nitrate, Hg2(NO3)2 + 4HCl = 2HgCl2 + 2H2O + 2NO2, and, commercially, by heating a mixture of mercuric sulphate and common salt, the mercuric chloride subliming and being condensed in the form of small rhombic crystals. It melts at 288°, and boils at 303°; it is sparingly soluble in cold water, more so in hot; it is very soluble in alcohol and ether. It is soluble in hydrochloric acid forming compounds such as HgCl2·2HCl, 3HgCl2·4HCl, 2HgCl2·HCl, according to the temperature and concentration; it also forms double salts with many chlorides; sal alembroth, 2NH4Cl·HgCl2·H2O, is the compound with ammonium chloride. It absorbs ammonia to form HgCl2·NH3, which may be distilled without decomposition. Various oxychlorides are formed by digesting corrosive sublimate with mercuric oxide. Corrosive sublimate has important applications in medicine—as an astringent, stimulant, caustic and antiseptic (see Mercury).