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.
We have already stated that in the hands of Dr. Hjaltelin and Dr. A. W. Foote, the internal use of sulphurous acid solution in smallpox was combined with the external application of the gaseous form, and, so far as could be judged, with good effect. The secondary fever of this malady is due to absorption from the pustular eruption, and this ought to be influenced by the early employment of such remedies, and I believe is so influenced. In one exceedingly severe case of confluent small-pox, considered hopeless by a good practitioner, the patient was enabled to take 1/2-dr. doses of sulphurous acid every hour or two, and within a short time showed signs of improvement, which went on to complete recovery, not in accord with the normal rate of progress in such cases. To variolous pustules maturating the acid with glycerin is a good application.