This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
In chancre, with phagedaenic ulceration, Ricord recommends a caustic paste made with sulphuric acid and charcoal to be applied on linen for several hours - until a slough forms. In hospital gangrene the pure acid has been successfully employed (Medical Times, i., 1859). For such purposes and for cancer, Sir J. Simpson mixed it with zinc sulphate. The reason for using powders, especially charcoal, to mix with the acid, is to secure a full strength in convenient form without dilution with water: Syme employed sawdust; Vel-peau, saffron.