This is also powerfully escharotic, though less so than the sulphuric acid. It stains the cuticle yellow before destroying it, and imparts the same hue to other tissues. It operates no doubt in some measure by oxidizing the constituents of the part destroyed. In its concentrated state, it has been used for denuding the cuticle, to destroy warts and the crusts of favus or porrigo, as an application to phagedenic ulcers, and to decompose the poison in the bites of rabid animals. It is said to be peculiarly useful in phagedenic ulcers, to the whole surface of which it is applied, so as to form a firm dry crust. To restrict its action, the parts around should be protected by resin cerate or plaster. Dr. Henry Smith, of London, strongly recommends it in certain cases of piles, with a prolapsed condition of the rectum, and an unhealthy and vascular state of the mucous membrane. The strong acid is applied freely to the diseased membrane, and occasions a good deal of pain at first; but, after the subsidence of this, there is little further suffering. (See Lond. Med. Times and Gaz., Aug. 1854, p. 185.)

Largely diluted, it has been used as a wash for indolent, carious, sloughing, and otherwise ill-conditioned ulcers; and, in the form of an ointment, in chronic skin diseases, especially impetigo in its advanced stages. (See vol. i. p. 311.)