Sulphurous Acid is the gas that is set free by burning sulphur. It is an old-fashioned disinfectant of great potency, and occasionally prescribed as an inhalant in place of those referred to above. Dissolved in water, and of certain strength, it retains the same name, and further diluted forms a valuable lotion in the treatment of ringworm, grease, and thrush. It is but rarely employed as an internal remedy, its action being very similar to carbolic preparations, but not as effectual in arresting the disengagement of intestinal gases.