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.
Moseley, in his work on tropical diseases, considers alum to be one of the best medicines in acute and chronic dysentery, and Dr. Waring has often seen it useful in asthenic cases; it was commonly given with opium. I think that a good mode of administering it in chronic cases is by injection, from 10 gr. to 2 dr. in a pint of liquid being used at a time (Hannon: Bulletin de l'Academie, xxxii.); this will also relieve the troublesome tenesmus, and the sense of itching and excoriation about the anus. One drachm to the pint is a proportion I have commonly used twice daily with good success: a strength of 1/2 oz. to the pint has also been used, but caused some burning pain; improvement, however, soon began, and cure resulted after about fourteen days of treatment (Medical Record, 1879).