Synonym. Hydrargyri Ammonio-Chloridum. Lond. Dub. Hydrargyri Praecipitatum Album. Edin.

Prep. Corrosive sublimate, three ounces; solution of ammonia, four ounces; distilled water, three pints. Dissolve the chloride in the water, aided by heat; to the solution, when it has cooled, add the ammonia, frequently shaking it. Collect the precipitated powder on a filter, and wash with distilled water until the liquid which passes through ceases to give a precipitate when dropped into a solution of nitrate of silver acidulated by nitric acid; lastly, dry it. When ammonia is added to a solution of corrosive sublimate, this peculiar compound, and not simply the oxide of mercury, is precipitated.

Prop. & Comp. A white, amorphous, heavy powder, usually in the form of small spiral cones from the wringing of the linen filters; when heated it sublimes; it is insoluble in water, alcohol, and ether; dissolves in hydrochloric acid without effervescence; and when heated with a solution of potash gives off vapours of ammonia, and becomes yellow from the formation of the oxide of mercury; and the resulting fluid, filtered and acidulated with nitric acid, gives a white precipitate with nitrate of silver. Boiled with a solution of chloride of tin, it becomes grey, and affords globules of metallic mercury. Its composition is represented by the formula, Nh2 Hg2 Cl. It may be regarded as a chloride of ammonium, in which two equivalents of hydrogen are replaced by two equivalents of mercury, or as a compound of chloride with amide of mercury (Hg Cl2 + Hg, Nh2). Some doubts exist as to its true chemical nature.

Off. Prep. Unguentum Hydrargyri Ammoniati. Ointment of Ammoniated Mercury.

Synonym. Unguentum Praecipitati Albi. Edin.

(Ammoniated mercury, sixty-four grains; simple ointment, one ounce.) [Ammoniated mercury, forty grains; ointment of lard, a troy ounce.]

Therapeutics. Never used internally; externally,it destroys pediculi, and acts as a stimulant application when used to chronic skin affections in the form of the ointment.

Adulteration. Chalk, carbonate of lead, plaster of Paris, etc.: these do not sublime when heated: the carbonates effervesce with acids.