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 any persistent articular inflammations, whether traumatic, gouty, or rheumatic, mercurial ointments or oleates are useful applied with friction two or three times daily. Mr. Scott (Bromley) earned a high reputation by his successful treatment of "white swelling," chronic synovitis, etc., with a mixture of mercurial ointment, camphor, soap, and cerate, applied on strips of lint firmly covered with plaster strapping. Although this method is useful I commonly prefer gentle friction with an ointment of the ammonio-chloride, beginning with a strength of 1 part of the officinal ointment to 4 of simple cerate, and using afterward 1 part in 8 two or three times daily. Under this simple treatment, with rest, I have known good results, which other remedies had failed to procure: thus, in one case of chronic inflammation of the wrist-joint, where able surgical and hydropathic treatment had been fairly tried, this ointment relieved more than any other means, and in several cases of chronic disease of knee-joint already condemned to amputation, the limb has been saved (though with stiffened joint) by this application.1
1 Mr. Marshall introduced, for these and other cases, the use of direct compounds of mercurial salts with oleic acid, as being "more elegant, economical, and efficacious." He recommends the yellow oxide to be precipitated by caustic potash from a solution in nitric acid, and then dissolved in oleic acid according to definite proportions - 5 or 10 per cent. or stronger; the weaker solutions are clear, pale, yellow liquids, the stronger are opaque and unctuous, and, being rather irritant, may cause pain. Mr. Marshall recommends 1 gr. of morphia to the drachm of ointment when much pain is present, as in pleuritis, and paints 10 to 30 drops over the affected part (Lancet, i., 1872). Morphia dissolves readily in oleic acid, and may thus be combined with the mercury.