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 cases of sloughing chancre, of phagedaena, of hospital gangrene, etc., when it is necessary to destroy portions of diseased tissue, and to stimulate to healthy action, strong nitric acid is one of the best caustics in use. The affected part should be cleansed and dried, so that the acid be not too diluted by secretion, the neighboring parts should be protected by oil or ointment, and the caustic then thoroughly applied with a glass brush, splinter of wood, or pledget of lint, until a firm dry yellowish mass is formed; the pain is at first severe, but soon subsides under cold water dressings, the eschar formed is not very deep, and usually separates in one or two days; the application may sometimes require to be repeated.
The combined internal and external use of tinct. ferri perchloridi is advised by Ricord (Medical Times, i., 1859). Roget adduced instances of it curing chancre when applied early, and he maintained that the local use of an acid solution directly after exposure would prevent gonorrhoeal, and even syphilitic contagion ("Traite sur le Perchlorure de Fer," 1860, Paris). Rabuteau speaks favorably of the remedy - substituting only citric acid for the more irritant hydrochloric. He adopts the following formula - R. Tinct. ferri perchloridi (30° Beaume, = 0.879 sp. gr.), 12 grammes; acidi citrici, 4 grammes; aquae, 24 grammes: solve f. lotio.