Gombault's Caustic balsam was a famous French Veterinary remedy that became quite popular in the United States through marketing by the Lawrence Williams Company of Ohio. This is basically a counter-irritant type of mediciation. It is thought that the formula for this medication is similar to the below as written in the Physicican's Formulary of 1912.
Croton oil. . . . . . . . . . . .4 drams
Cotton seed oil. . . . . . . . 2 oz.
Oil of camphor. . . . . . . . .1 dram
Oil of turpentine. . . . . . . . 1/2 dram
Kerosene. . . . . . . . . . . . .4 dram
sulphuric acid. . . . . . . . . .20 minims
To the mixture of croton and cotton seed oils, add the sulphuric acid, stirring continually, then add the other constituents. After standing a few days, it resembles the original preparation fairly well. -- (Western Druggist)
There is a lot of evidence on the internet that colza oil was the original oil used in the French version of this formula. Colza oil is the same thing as Cannola oil. I would think Cannola oil could be used as well as the above listed cottonseed oil. Much easier to fine!
Oil Of Croton. . . . . . . . A fixed oil expressed from the seeds of Croton Tiglium which naturally inhabits India and the Philippine Islands. It is a powerful purgative, irritant poison, rubefacient--all due to local action. Internal overdoses can cause death. It has been used externally for neuralgia, glandular swellings, pulmonary troubles, and pluerisy. One often can apply .06 to .13 cc of the oil directly to the skin's surface or infuse it in ether, chloroform, olive oil, soap liniment, oil of turpentine as a carrier. Another common horse medication that contained croton oil was Dr. Smith's Vita Oil which was very good when applied to stifles and rear-ends.
Cotton Seed Oil. . . . . . . . obviously it is the expressed oil obtained from the cotton plant seed. It has been used for years as a wholesome and digestible food, and is employed in pharmacy, medicine, and surgery in the old days for many of the purposes for which olive oil is employed. In this formula, it is used as a carrier oil.
Oil of Camphor. . . . . . . . . synthetic forms are often imployed today, but years ago it was obtained from the camphor laurel, Cinnamomum Camphora a large tree indigenous to Formosa, Japan, and China. Essential oil of camphor is employed as a rubefacient and mild counter-irritant to rheumatic and inflamed joints. It may be applied undiluted, or mixed with an equal quantity of olive oil. It is also used as a parasiticide.
Oil of Turpentine. . . . . . . . . Oil of turpentine is the volatile constituent of the oleoresinous exudate obtained from coniferous trees and known as turpentine. The oil is separated by distillation with water or steam; the residue in the still is known as rosin. By subjecting turpentine to a dry heat, an empyreumatic oil is produced, to which the term resin oil is more properly applied. Official oil of turpentine is a thin, colorless liquid, having a characteristic odor and taste, both of which become stronger and less pleasant by age and exposure to the air. From the King's American Dispensatory: "Externally it is a rubefacient, and is used as a counter-irritant in the form of liniment in rheumatism, paralysis, neuralgia, inflammation of internal organs, in the neighborhood of indolent tumors, to chilblains, indolent and erysipelatous ulcers, caries, sloughing, especially from pressure in exhausting diseases, gangrene, chronic inflammation of the edge of the eyelids, and, combined with linseed oil, in recent burns or scalds.
Kerosene. . . . . . . . . it is the light fraction petroleum product refined from the raw petroleum and used as a common lighting and cooking fuel.
Sulphuric acid. . . . . . . I would suspect this to be diluted sulphuric acid at 10%.