This is prepared, according to the directions of the U. S. Pharmacopoeia, by dissolving three troyounces of mercury in five troyounces of nitric acid, diluted with six fluidrachms of distilled water, and evaporating to the bulk of seven troyounces and a half. The preparation consists of deutoxide of mercury neutralized by nitric acid, with a considerable portion of the acid in excess.

It is a powerfully irritant and caustic liquid, highly esteemed by some practitioners. it is employed in lupus, in which it is considered as one of the best applications, in ulceration of the neck of the uterus, in cancerous and sloughing ulcers, carbuncles, moles, naevi materni, etc. To hasten or abort the indolent pustules of acne, and to produce a similar effect in large furuncles, it has also been recommended; a minute drop in the former, and a full-sized drop in the latter, being applied, by means of a line brush, to the apex of the tumours. {Med. Times and Gaz., Jan. 1855, p. 9.) in all these cases, the liquid caustic is best applied by means of a glass brush, which is unaffected by the acid. it has sometimes produced ptyalism, through absorption.