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.
By adding a concentrated solution of bismuth in nitric acid to an excess of carbonate of ammonia in cold solution.
The salt which precipitates is a hydrated oxycarbonate, which is, like the subnitrate, insoluble in water, but is more soluble in the gastric juice, and has antacid properties.
On passing a current of sulphuretted hydrogen through an acid solution of a bismuth salt, the black sulphide of bismuth (Bi2S3) will be thrown down. Concentrated acid solutions of bismuth salts poured into water give a white precipitate of subsalt, e.g., the nitrate when thus treated yields the subnitrate. Caustic alkali added to a solution of a bismuth salt precipitates the white hydrate of bismuth (Bi2O3H1O). Papers saturated with sulpho-cyanide of potassium are colored yellow by soluble bismuth salts.
Bismuth, in substance, is not absorbed by the skin, and the supposed instances of poisonous effects from its use as a cosmetic are not trustworthy (Husemann). A soluble bismuth salt, such as the ammonio-citrate, is, however, quickly absorbed from the cellular tissue after hypodermic injection.
Much difference exists in the degree of absorption of bismuth compounds taken by the mouth, and the difference is proportionate to their solubility. The acetate, the double tartrate, and the ammonio-citrate dissolve in the gastric fluids, and are readily absorbed, while the oxide and subcarbonate are but slightly soluble, and the ordinary subnitrate still less so.
Headland taught that it was as insoluble as charcoal, but Orfila and Lewald have detected the drug in the liver, in the milk, and the urine, after its administration, though in the latter secretion it appeared later than other metallic salts usually do. Bergeret and Mayencon detected it in the same fluids, and in the serous exudations of dropsy, and after giving small doses to rabbits they found it, within half an hour, in the blood, the spleen, the muscles, etc., and continued to find traces of it for eight days after administration. In one man they also found it five days after; in another, testing sixty-two days afterward, they did not find any (Journal de l' Anatomie, 1873). We may conclude, therefore, that some amount of absorption even of the subnitrate occurs (and probably as chloride), although the greater part of what has been taken has been found unchanged in the stomach in some cases, or altered to a bluish tint in the small intestine, or converted into the black sulphide in the colon or rectum, or has been eliminated with the faeces during life. Dr. Levick mentions a case of phthisical diarrhoea, in which 20 gr. were taken four times daily for some weeks, and the whole intestinal canal was found to be lined by the bismuth powder (American Medical Journal, July, 1858). It is probable that more absorption occurs with small doses (such as the grain or less used originally by Odier, of Geneva), than with the very large ones (several hundred grains daily) prescribed by Monneret.
The pulverulent bismuth compounds have an absorbent and protective effect: they are also somewhat astringent and sedative. The crystallized nitrate, especially when dissolved in glycerin, is also astringent, but is more irritating, even somewhat caustic.