Protochloride of Mercury

Synonyms.—Mercurous Chloride Protochloride of Mercury Calomel. 

Provided no easily reduced metel be contained in the substance to be assayed, a quicker method may be resorted to. It consists in adding to the solution of the compound, as free from nitrio acid as possible, protochloride of fin, acidulated with hydrochloric acid, and collecting the precipitated mercury on a weighed filter, washing and drying under ths exhausted receiver, over sulphuric acid, and weighing. 

SYNS CALOGREEN CALOMEL CALOMEU NO (ITALIAN) CALOSAN CHLORURE MERCUREUX (FRENCH) C.I. 77764 CLORURO MERCUROSO (ITALIAN) CYCLOSAN KALOMEL (GERMAN) MERCUROCHLORID (DUTCH) MERCURY)]) CHLORIDE MERCURY MONOCHLORIDE MERCURY PROTOCHLORIDE MILD MERCURY CHLORIDE PRECIPITE BLANC QUECKSILBER(I)-CHLORID (GERMAN) QUECKSILBER CHLORUER (GERMAN) SUBCHLORIDE of MERCURY... 

To prepare it, protochlftride of mercury (calomel) is rapidly mixed with aqua potasses in excess, by rubbing in a mortar and the black powder formed is washed with cold water and dried in the dark. HgCl + KO = KCl + HgO. It is a black or dark olive powder, which is easily resolved into peroxide and metal 2 HgO = HgO + Hg and hence is difficult,to keep. It is a feeble base, and forms with acids ciystaUisable salts, such as the acetate and nitrate. Its solutions are precipitated black by caustic alkalies white (calomel) by hydrochloric acid, or a soluble chloride and the metal is reduced by copper, phosphorous acid, or protochloride of tin. 

Syn. Calomel—Occurs sparingly as horn quicksilver in the mineral kingdom. May be prepared either by subliming a mixture of bichloride of mercury and mercury, HgCl, -j- Hg, which yields 2 HgCl or by adding hydrochloric acid or solution of common salt to a solution of protonitrate of mercury, when the protochloride is precipitated. HgO, NOj - - NaCl = NaO, NO, - - HgCl. It is a heavy white volatile powder, insoluble in water. It is blackened by alkalies. When first prepared, it is always contaminated with corrosive sublimate, and must be well washed with hot water before it is used as a medicine. 

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