Is soluble only in 800 parts water, but the bisulphite and hyposulphite are freely soluble.

Absorption And Elimination

Sulphurous acid is readily absorbed, and its characteristic odor has been observed in the breath and secretions after its administration (Dr. George Wilks: British Medical Journal, ii., 1870). It passes out also with the urine and faeces as sulphate or sulphuric acid, for it is readily oxidized in the system.

The sulphites are decomposed in the stomach by the gastric acid, sulphurous acid is given off, and they are mostly changed into sulphates (Kletzinsky), and are eliminated as such, partly by the intestinal canal, but chiefly by the kidneys (Bartholow); they pass within twelve to twenty-four hours after administration (Polli).

The hyposulphites undergo similar changes, but more slowly, for they are more stable.

After very large doses, these salts may be found unchanged in the urine (Rabuteau), and, after their application to wounds, free sulphuric acid may be traced in the same secretion (De Ricci).

Physiological Action (External)

Externally applied, sulphurous acid is refrigerant, somewhat astringent, and in full strength irritant. The most important property of the gas and its compounds is that of arresting fermentation, and of destroying the lower forms of vegetable and animal life, and certain infective organic poisons. Its power of controlling ferments and destroying visible parasites is readily proved, but its action on infectious organic particles - a true "disinfectant" action, by which they are rendered inert - is not so capable of demonstration, because the poison itself, the essence of infection, has not yet been verified and isolated; still, as Dr. Sansom observes, "we know that such poison is ponderable, that it obeys physical laws, and is active for long periods, though so minutely divided as to be undemonstrable by ordinary direct physical means" (British Medical Journal, ii., 1872). The diffusion-experiments of Chauveau and Sanderson have proved, at least for vaccinia, variola, and sheep-pock, that the poison is solid, insoluble, and indiffusi-ble; and, to judge from its effects, its extraordinary power of multiplication, etc., either it must have some properties of living matter, or act by a process of catalysis or fermentation: the former seems more likely, but however it be, if we make evident that sulphurous acid can prevent or arrest the development of the bacteria, monads, and germs of fungi, etc., which accompany decomposition, it is by analogy probable that it can exert a similar effect on the minuter particles which constitute infective poison. In proof of the former fact, among other experiments, Dr. San-som placed cubes of egg-albumen under glass covers with solutions of permanganate, of aluminium chloride, of carbolic and sulphurous acids; and, with the two latter agents, notably with the last, secured almost complete preservation, even after the admission of air (British Medical Journal, loc. cit.). For aerial disinfection, Hoppe-Seyler, after careful trial, found sulphurous acid gas the best agent, - 1 or 2 per cent. of it in the air of a room destroying all the lower organisms: this could be secured by burning 1/2 to 1 dr. of sulphur for each 100 cubic feet of space (Lancet, ii., 1871, p. 304).

Letheby arrived at similar conclusions, but recommended, for greater security, a larger proportion of sulphur - 1 1/2 oz. - to each 100 cubic feet of air (Medical Times, ii., 1873).

Dr. Baxter, taking up the same question from another point of view, concluded not only that sulphurous acid was the best of aerial disinfectants, but that its action on vaccine virus was more potent than that of chlorine or carbolic acid. Thus he vaccinated one arm of a child with points of virgin lymph, and the other arm with points previously exposed to the action of the three agents, and while small vesicles often resulted after the use of chlorine or carbolic acid, none could be obtained after sulphurous acid, "even under conditions which seemed to render the virulent particles least susceptible to destructive influences" ("Sixth Report of Medical Officer Privy Council," N. S., and Lancet, i., 1876). It is true that Dr. Dougall had found sulphurous not so effective as other mineral acids (notably chromic acid) in preventing the decomposition of organic solutions, but Crace Calvert showed this was not correct, and 1 part of the former in 1,000 of albuminous solution was enough to preserve it for forty days, while other acids only preserved it for nine or ten days. Dr. Fergus also compared glasses of beef extract heated with sulphurous acid, carbolic acid, and terebene, and found several weeks afterward that the one heated with sulphurous acid remained quite sweet while the others were decomposed (Practitioner, i., 1877).

Physiological Action (Internal)

From the preceding and many other observations, there can be no doubt of the disinfectant power possessed by sulphurous acid in a very high degree when brought into direct contact with infective or putrescent material, whether in the air, or in wounds, etc., but the further question whether it can be so introduced into the circulating blood of living animals as to neutralize a septic poison therein also circulating, or so as to prevent the admission of such poison, is more difficult to resolve. Dr. Polli (Milan) held the affirmative to be proved by his experiments upon dogs with sulphites and hyposulphites; after treating an animal with these medicines, he injected septic poison, and found it did not succumb to the effects, while a healthy but untreated animal quickly did so. In other cases, examining the bodies of animals killed after sulphite treatment, they were found to decompose much less quickly and less readily than others not so treated. He offered, also, some clinical evidence of the value of these remedies in septicaemia, and much practical benefit was expected from his observations; they have not, however, yet passed the region of controversy. Semmola, O. Weber, and others, deny them, or characterize them as "negative." Clinical results differ, and although I hold that much may be done by introducing "disinfectant" medicines, especially sulphurous acid, into the organism, I acknowledge that definite proofs of their power and mode of action within it are still to be desired (v. p. 243, also Carbolic and Salicylic Acids).