Dose. - 1/2-1/2 grain (0.01-0.03 Gm.) [1/5 grain (0.01 Gm.), U. S. P.].

Hydrargyri Iodidum Rubrum - Hydrargyri Iodidi Rubri - Red mercuric Iodide (U.S. P.) (Biniodide of Mercury - Red Iodide of Mercury). - Origin. -Prepared by mixing solutions of corrosive mercuric chloride and potassium iodide; filter, and dry the precipitated red iodide. It should contain not less than 99.5 per cent. of pure mercuric iodide.

Description and Properties. - A scarlet-red, amorphous powder, odorless and tasteless; permanent in the air. Almost insoluble in water, but soluble in 130 parts of alcohol. It should be kept in well-stoppered bottles, protected from light.

Dose. - 1/32-1/16 grain (0.002-0.004 Gm.) [1/20 grain (0.003 Gm.), U. S. P.].

Liquor Arseni et Hydrargyri Iodidi - Liquoris Arseni et Hydrargyri Iodidi - Solution of Arsenic and Mercuric Iodide. - (Described under Arsenic.) - Dose, 5 minims (0.3 Cc), gradually increased.

Hydrargyri Oxidum Flavum - Hydrargyri Oxidi Flavi - Yellow Mercuric Oxide (U. S. P.). - Origin. - Prepared by precipitating a solution of corrosive mercuric chloride with soda. It should contain not less than 99.5 per cent. of pure yellow mercuric oxide.

Description and Properties. - A light orange-yellow, amorphous, heavy, impalpable powder; odorless, and having a somewhat metallic taste. Permanent in the air, but turning darker on exposure to light. Almost insoluble in water or in alcohol. It should be kept in well-stoppered bottles, protected from light. Not used internally.

Unguentum Hydrargyri Oxidi Flavi - Unguenti Hydrargyri Oxidi Flavi -Ointment of Yellow Mercuric Oxide. - Formula: Yellow mercuric oxide, 10; water, 10; hydrous wool-fat, 40; petrolatum, 40. Used externally.

Hydrargyri Oxidum Rubrum - Hydrargyri Oxidi Rubri - Red Mercuric Oxide (U. S. P.) (Red Precipitate). - Origin. - Prepared by dissolving mercury in diluted nitric acid. Evaporate to dryness. Triturate the mercuric nitrate thus formed with mercury and heat. It should contain not less than 99.5 per cent. of pure red mercuric oxide.

Description and Properties. - Heavy, orange-red crystalline scales, or a crystalline powder, becoming yellower the finer it is divided; odorless, and having a somewhat metallic taste; permanent in the air. Almost insoluble in water and in alcohol. It should be kept in well-stoppered bottles, protected from light.

Dose. - 1/64-1/10 grain (0.001-0.006 Gm.).

Unguentum Hydrargyri oxidi Rubri - Unguenti Hydrargyri Oxidi Rubri -Ointment of Red Mercuric Oxide. - Formula: Red mercuric oxide, 10; water, 10; hydrous wool-fat, 40; petrolatum, 40. Used externally.

Liquor Hydrargyri Nitratis - Liquoris Hydrargyri Nitratis - Solution of Mercuric Nitrate (U. S. P.). - A liquid containing about 60 per cent. of mercuric nitrate, together with about 11 per cent. of free nitric acid.

Description and Properties. - A clear, nearly colorless, heavy liquid, having a faint odor of nitric acid and a strongly acid reaction. The product should be kept in glass-stoppered bottles.

Used externally as a caustic.

Unguentum Hydrargyri Nitratis - Unguenti Hydrargyri Nitratis - Ointment of Mercuric Nitrate (U. S. P.) (Citrine Ointment). - Formula: Mercury, 70; nitric acid, 175; lard, 760 parts. Used externally.

Unofficial Preparations

Lotio Flava - Lotionis Flavae - Yellow Wash. - Corrosive sublimate, 25 grains (0.5 Gm.), in lime water, 16 ounces (473.17 Cc). For external use.

Lotio Nigra - Lotionis Nigrae - Black Wash. - Calomel, 64 grains (4.15 Gm.), in lime water, 16 ounces (473-17 Cc). For external use.

Asparagin Hydrargyrate. - Dose. - 1/6 grain (0.01 Gm.), hypodermically.

Antagonists and Incompatibles. - Mercury with chalk is incompatible with acids and acidulous salts. Calomel is incompatible with alkalies, alkaline earths, alkaline carbonates, iron, lead, copper, iodine, bromides, soaps, sulphydrates, and nitrohydrochloric acid, as well as hydrochloric acid, potassium, ammonium, and sodium chloride.

Corrosive sublimate is incompatible with alkalies and their carbonates, soap, lime water, tartar emetic, the iodides of potassium and sodium, acetate of lead, silver nitrate, the sulphides, albuminous liquids (as milk, etc.), many vegetable infusions, and compound syrup of sarsaparilla.

In general, metallic preparations of mercury are incompatible with iodine and the chlorides.

Synergists. - Potassium iodide enhances the antisyphilitic action of mercury. Depressants - such as antimony and alkalies - increase the physiological activity of mercury and its preparations.

Tonic and resin-bearing purgatives - such as aloes, rhubarb, and podophyllum - aid the cathartic action of some of the mercurial preparations.

Physiological Action. - Externally and Locally. - Most of the preparations applied to the skin are antiparasiticide and antiseptic, corrosive mercuric chloride being one of the most important antiseptics and universal germicides known.

Some of the mercurials are powerful irritants, the nitrate being an active caustic. The mercurous salts even possess slightly stimulating properties.

Metallic mercury and its salts are readily absorbed with the aid of friction, at times producing a slight irritation resulting from their stimulating properties. Absorption may also take place from local application in the form of a fine vapor.

The introduction of the drug into the system through the medium of the skin is attended with all the symptoms of mercurial poisoning. The local actions of the various preparations differ somewhat, yet they agree in certain physiological effects produced after absorption of the drug.

Locally, on mucous membranes, mercury acts as an astringent or cauterizant, according to the salt used and the grade of concentration. The mercury ion has a marked affinity for albumin, coagulating it. The coagulum is usually light and flocculent, and the action of the metal is thus made more penetrating. In contact with mucous membranes an albuminate is formed which is very soluble in an excess of proteid. Thus absorption is rapid.