This section is from the book "Materia Medica And Therapeutics: An Introduction to the National Treatment of Disease", by John Mitchell Bruce. Also available from Amazon: The pharmacology and therapeutics of the materia medica.
Dose. - 10 to 60 gr.
Sulphurous acid is a powerful deoxydising agent. Seizing on oxygen and water, it decomposes organic bodies, and at the same time produces upon them the irritant local effects of sulphuric acid, into which it is converted. It thus destroys low forms of living matter, including the organisms associated with fermentation, decomposition, and certain diseases, 1 part in 666 of water being sufficient for this purpose. Sulphurous acid is therefore applied to ringworms and foul wounds; and some kinds of sore throat are relieved by a spray of the officinal acid. Morbid fermentation in the stomach attended by the growth of organisms, such as penicillium and sarcina, may be quickly arrested by doses of min. 5 to min. 60 of the officinal acid; but the non-officinal salts are more convenient forms for internal use, being decomposed by the acids of the stomach. Sulphites given in full doses become converted into sulphates, and act as purgatives.
Sulphurous anhydride, although not officinal, is very extensively used for fumigating infected rooms and clothing, being probably the most powerful, certain, and convenient of all disinfectants. Sulphur is burned on a shovel or plate, the outlets from the room having been carefully closed, excepting the door through which retreat is made.
The evidence, however, is to the effect that sulphites are not absorbed as such, but as sulphates, and the benefit derived from them in fevers is probably due to the laxative and diuretic effects of the higher salts. The suggested decomposition of hyposulphites into sulphites and free sulphur, and their consequent alterative and disinfectant action in phthisis and other diseases, appear to be equally unreal.
Sulphites are excreted by the urine and bowels in the form of sulphates.