Lond

Bichloride of Mercury.

Syn. Corrosive Sublimate.

This has been described among the preparations of mercury (ii. 307). Locally, it is irritant, and, in a concentrated state, moderately caustic. As corrosive sublimate has a strong affinity for albumen, it is not impossible that it may operate chemically as an escharotic; but I am disposed to think that its action is in part at least dynamic; as it is a powerful local irritant, and its corrosive effect is greater upon diseased than sound tissue. it is seldom used as an escharotic; but chiefly as a stimulant and alterative application in cutaneous eruptions, chronic mucous inflammation, and indolent or specific ulcers.

There is, however, one affection, in which, from considerable experience of its good effects, I would strongly recommend it, with a view to its caustic operation. Under the name of onychia maligna, we occasionally meet with an extremely obstinate ulcer, situated around the nail of a finger or toe, attended with considerable swelling, of a fetid odour and very ill-conditioned appearance, frequently separating the nail, and seeming to have no tendency to heal. Formerly it was deemed necessary sometimes to amputate the finger or toe. 1 have never met with a case which refused to yield to the following treatment, which originated with the late Dr. Perkins, of Philadelphia, and was strongly recommended by Dr. Physick in his lectures. Equal parts of corrosive sublimate and sulphate of zinc, well powdered, are intimately mixed; the mixture is sprinkled thickly on the ulcerated surface, so as to cover the whole of it deeply; a pledget of lint thoroughly wet with tincture of myrrh is placed over the powder; and the whole dressed with a compress and bandage. it is of little consequence what alcoholic liquid is used; the object of it being that it should act as a solvent to the mercurial salt. I have generally substituted laudanum for the tincture of myrrh. Severe pain is experienced, which ceases in half an hour or less; and, upon the removal of the dressings, some hours afterwards, an eschar is seen to have formed, covering the whole surface of the ulcer. This is thrown off in the usual time, and a healthy surface left, which heals without difficulty. The peculiar merit of the preparation seems to be, that the escharotic, dissolved by the alcoholic liquid, penetrates to every part of the diseased structure about the root of the nail, and everywhere destroys it. Little effect is produced upon the sound flesh. Whether the chloride would answer the same purpose without the salt of zinc, I do not know; for I have never tried them separately.

As a local stimulant and alterative, corrosive sublimate is a good deal used. Dissolved in water, in the proportion of from five to ten grains to the fluidounce, it is an excellent application to syphilitic ulcers of the fauces, or secondary ulcers of the same character elsewhere, which seem indisposed to heal under constitutional treatment alone. it should be applied by means of a camel's-hair pencil, so as not to touch the sound parts. Employed in the same way, it would probably prove useful in other indolent and ill-conditioned ulcers. A weaker solution, containing one or two grains to the fluidounce, may be used as a lotion for indolent cutaneous affections, requiring a gentle stimulation. it may be used in lepra and psoriasis, and in acne to hasten the suppuration. The same solution has been employed to destroy insects ill the hair, in different parts of the body. A still weaker solution, containing from an eighth to half a grain in the fluidounce, is used as a collyrium in chronic and syphilitic ophthalmia, as a gargle in venereal sore-throat, and as an injection in gleet and leucorrhoea. The addition of alcohol facilitates the solution of the salt in water, and, when it is used in large proportion, this addition may be usefully resorted to.

Trousseau and Pidoux insist strongly on the efficacy of a solution of this salt in pruritus of the vulva. They dissolve 1 part of corrosive sublimate in 100 parts of alcohol, and direct a fluidrachm of the solution to be added to a pint of hot water, which is to be employed as an injection or lotion, as hot as it can well be borne. {Trait, de Thérap., 4e ed., i. 206.)

The use of this salt in baths has been already noticed (II. 303).