Liquor Hydrargyri Bichloridi

Lond.

Solution of Bichloride of Mercury,

"Take of bichloride of mercury, hydrochlorate of ammonia, each ten grains; distilled water, a pint Dissolve the bichloride of mercury and the hydrochlorate of ammonia in the water."

This solution is intended to facilitate the administration of minute doses of bichloride of mercury, each fluid ounce of the solution containing half a grain of the salt. It ought not

1 Pearson on Remedies for Lues Venerea, etc. 116.

2 Willan on Cutaneous Diseases, 140.

to be long kept or exposed to a clear light, as the bichloride is gradually decomposed, and calomel precipitated. It is, however, the most safe and convenient form of administering this active salt; and it may be given as an antisyphilitic in doses of from f 3ss. to 3ij f ij. of linseed infusion, or of water and syrup, and in more minute doses, when its alterative effects only are required. As a local application, this solution, diluted with two parts of water, forms a useful gargle in venereal sore throat; and without dilution we have found it serviceable as a gargle for breaking the abscess in cynanche tonsillaris, when suppuration takes place. Diluted with an equal quantity of water, it is employed as a wash against tetters and scabies; and very largely diluted, it may be used as an injection in gonorrhoea; and given in the form of enema, when the stomach will not receive it. With lime-water, in the proportion of gr. j. of the salt to f j. of lime-water, it forms the yellow wash.

Hydrargyri Bicyanidum. Lond. Bicyanide of Mercury

"Take percyanide of iron, eight ounces; binoxide of mercury, ten ounces; distilled water, four pints. Boil them together for half an hour, and filter. Evaporate the solution that crystals may form. Wash, frequently, what remains with boiling distilled water, and again evaporate the mixed liquors that crystals may be formed.

"Bicyanide of mercury may be also prepared by adding as much binoxide of mercury as will accurately saturate hydrocyanic acid, distilled from ferrocyanide of potassium, with diluted sulphuric acid."

In this process, the Prussian blue and binoxide of mercury are reciprocally decomposed: the cyanogen of the former quitting the iron combines with the mercury of the binoxide, whilst the oxygen of the latter combines with the iron of the percyanide, and forms a sesquioxide of iron. The two new compounds are easily separated, owing to the solubility of the bicyanide of mercury, and the insolubility of the sesquioxide of iron, which remains upon the filter.

The second process is as easily explained. The oxygen of the binoxide unites with the hydrogen of the hydrocyanic acid, whilst the cyanogen combines with the mercury: two equivalents of the acid being required to decompose one of the binoxide, a bicyanide is the result.