Prep. Mercury, four ounces; nitric acid, three fluid ounces and a quarter; distilled water, three fluid ounces. Mix the nitric acid and the water, and dissolve the mercury in the mixture without heat; afterwards boil gently for fifteen minutes, cool and preserve in a stoppered bottle.

[Liquor Hydrargyri Nitratis. Solution of Nitrate of Mercury.

U. S. Mercury, three troy ounces; nitric acid, five troy ounces; distilled water, six fl. drachms. Dissolve the mercury with the aid of a gentle heat, in the acid mixed with the water. Afterwards evaporate to seven troy ounces and a half. Sp. gr. 2.165.]

Prop. & Comp. Nitrate of Mercury (Hg O, No5) in solution in nitric acid. It forms a colourless, strongly acid solution, which gives a yellow precipitate with potash added in excess. If a crystal of sulphate of iron be dropped into it, in a little time the salt of iron and the liquid in its vicinity acquire a dark colour. Sp. gr. 2.246. A little of it dropped into hydrochloric acid when diluted with twice its volume of water gives no precipitate.

Off. Prep. Unguentum Hydrargyri Nitratis. Ointment of Nitrate of Mercury.

Synonym. Unguentum Citrinum. Edin.

(Mercury, by weight, four ounces; nitric acid, eight fluid ounces; prepared lard, fifteen ounces; olive oil, thirty-two fluid ounces. Dissolve the mercury in the nitric acid with the aid of a gentle heat, then add the solution to the lard and oil, previously melted together by a steam or water-bath, and mix thoroughly. If the mixture do not froth up, increase the heat till this occurs.)

Therapeutics. The acid solution of nitrate of mercury is a powerful caustic, and has been applied topically in some cancerous affections and in lupus. The ointment acts as a stimulant, and is used in skin affections, and especially in chronic inflammatory diseases of the eyes, as in Ophthalmia Tarsi, etc. The ointment can be diluted to any degree.

Dose. The acid solution is not intended for internal adminis-tration.