This metallic salt is by far the most active of all the mercurial preparations. According to the latest views of Chemistry it is a compound of two proportionals of chlorine, and one proportional of metallic mercury, and is therefore a _bi-chloride of Mercury_. It generally occurs in the form of a crystalline mass, made up of very small prismatic crystals, which undergo a slight alteration by exposure to air, becoming opaque and pulverulent. Its taste is extremely acrid, with a metallic astringency, occasioning a sensation of obstruction in the throat which continues for some time. Its specific gravity is 5·1398[268]. When pulverised and thrown upon burning coals, it is immediately volatilized, giving out a thick white smoke, of a very pungent smell, not at all resembling garlic, but which irritates the mucous membranes extremely, and is highly dangerous to those who breathe it. It is soluble in eleven parts of cold, and in three of boiling water; and this solubility may be farther increased by the addition of a few drops of rectified spirit, or of muriatic acid. When swallowed in small quantities it acts as a most virulent poison.[269] _Symptoms of Poisoning by Corrosive Sublimate._ The effects, as well as the _modus operandi_, of this salt, will vary with the quantity swallowed. We shall, therefore, first consider the acute symptoms which supervene a dose sufficiently powerful to destroy life in a few hours; and afterwards those which may arise from its long continued use in small quantities, and at different intervals. 1. _Symptoms which follow a large dose._ A most painful burning and sense of constriction is experienced in the fauces; dryness of the mouth and lips; excruciating pain in the stomach and bowels, increased by the slightest pressure, and generally attended with considerable distention; excessive vomiting and purging of frothy mucus; the countenance is frequently red and swollen, and the eyes exhibit a sparkling appearance, accompanied by contraction of the pupils. The pulse is in general quick, small, and hard; suppression of urine takes place, and cold sweats; anxiety; universal pains; convulsions, and death. If the patient survives long enough, a violent ptyalism, and sloughing of the mouth and gums may take place.