462

ELEMENTS OF MATERIA MEDICA.

venereal diseases, but is objectionable, especially where the bowels aremorbidly irritable. It is rarely or never used now.

In pharmacy it is employed in the preparation of bicyanide of mercury[vide Hydrargyri Bicyanidum).

Administration. —The dose of it is from a quarter of a grain to agrain, given in the form of pill, in combination with opium.

Lotio Flav a : Lotio (seu aqua) phagedcenica: yellow wash. —Thiscompound, which was formerly in frequent use, is prepared by addingbichloride of mercury to lime-water. The proportions vary in differentformulas. The quantity of bichloride should not, I think, exceed twograins to an ounce of lime-water: the usual proportions are thirty grainsof bichloride to sixteen ounces of lime-water. The preparation, then,consists of the yellow hydrated binoxide of mercury (which precipitates),chloride of calcium, and caustic lime ; the two latter being in solution.But if the quantity of bichloride exceed 3 X 7 ^ grains to an ounce of lime-water, the precipitate is brown or brick-dust coloured, and containsoxichloride of mercury, while the clear liquor holds in solution somehydrargyro-chloride of calcium ; that is, a saline combination, in whichchloride of calcium is the base, and bichloride of mercury the acid(Guibourt, Journ. Chim. Med. iii. 377; also Pharm. Raisomee, i. 563;and Souberain, Nouv. Traite de Pharm. ii. 529). Yellow or phagedenicwash is applied, by means of lint, to venereal and scrofulous ulcers.Dr. Hintze (j Brit, and For. Med. Rev. April 1836) used it with advantagein chronic ulcers which succeed to burns. It should be well shaken,and used in the turbid state.

Hydrar'gyri-Ni'trico-Ox'ydum, — Ni'tric-ox'ide of Mercury.

History. —This preparation was known to Raymond Lully in thelatter part of the thirteenth century. It is commonly termed red pre-cipitated mercury [mercurius preecipitatus ruber), or, for brevity, red pre-cipitate. It is the oxidum hydrargyrum rubrum per acidum nitricum ofthe Edinburgh Pharmacopoeia.

Preparation. — In the London Pharmacopoeia this compound isdirected to be prepared by dissolving three pounds of mercury in a mix-ture of a pound and a half of nitric acid and two pints (3x1.) of distilledwater. The solution is to be evaporated to dryness, and the residnereduced to powder; which is to be put in a shallow vessel, and heated bya slow but gradually increased fire, until red vapours cease to arise.

This compound is best prepared on the large scale, for it cannot be sowell procured of the bright orange-red colour and crystalline or scalyappearance usually considered desirable, when only small quantities ofmaterials'are employed. Some advise a larger quantity of nitric acid tobe employed than is directed in the London Pharmacopoeia. The reduc-tion of the nitrate to powder is objectionable, as it diminishes thecrystalline appearance of the oxide. Mr. Brande ( Manual of Chemistry)says, “ the nitrate requires to be constantly stirred during the process,which is usually performed in a cast-iron pot.” But in general a shallowearthen dish is employed, with a second one inverted over it, and care istaken not to disturb the nitrate during the operation. The heat of thesand-bath is employed. Indeed, some have asserted that the finest