Synonym. Hydrargyri Bichloridum. Lond.

Prep. Sulphate of mercury, twenty ounces; chloride of sodium, dried, ten ounces; black oxide of manganese, in fine powder, one ounce. The sulphate and the chloride are reduced to fine powder, and then thoroughly mixed by trituration in a mortar with the oxide of manganese and the corrosive sublimate sublimed. When the sulphate of mercury is heated with the common salt, a double decomposition takes place; and chloride of mercury, and sulphate of soda are produced, as represented in the formula, Hg O, So3 + Na Cl=NaO, So3 + Hg Cl.

Prop. & Comp. Corrosive sublimate occurs in heavy white crystalline masses of a styptic and metallic taste. Composition (Hg Cl); soluble in about 20 parts of cold water; much more so in alcohol; soluble also in ether: melts and entirely sublimes when heated. Its watery solution is precipitated by alkalies and lime-water, of a red or yellowish colour (the oxide); when this precipitate is heated, it gives off oxygen, and runs into globules of metallic mercury: the solution of corrosive sublimate gives a white precipitate with ammonia, and a curdy white precipitate with nitrate of silver; it precipitates albumen, and forms with it a definite and very sparingly soluble compound. When heated, chloride of mercury sublimes without decomposition, leaving no residue. Hydrochlorate of ammonia increases the solvent power of water for corrosive sublimate.

Therapeutics. Corrosive sublimate is a very powerful irritant; when taken in large doses, it causes burning at the epigastrium, vomiting and purging; applied to the skin, it acts as a corrosive. In very small doses it is useful as an alterative in chronic affections, syphilitic or not, as in scaly skin diseases, periosteal affections, etc.; externally, as a lotion, injection, gargle, or ointment, in chronic skin diseases, ulcerated sore throats, and chronic discharge from mucous membranes. All the ordinary effects of mercury may be produced by this salt.

Dose. 1/20 gr- to 1/4 gr. in solution or pill, with crumb of bread.

Incompatibles. In solution it precipitates most of the vegetable preparations which contain albumen, tannin, etc. It is also thrown down by alkalies, alkaline sulphurets, iodides, and tartar emetic. An iodide in excess redissolves the precipitate.