What is "h2so3"

Sulphurous \Sul"phur*ous\, a. [L. sulphurosus, sulfurosus: cf. F. sulfureux.]

1. Of or pertaining to sulphur.

2. (Chem.)

   1. Derived from, or containing, sulphur; specifically, designating those compounds in which the element has a lower valence as contrasted with the sulphuric compounds.

   2. Having the characteristic odor of sulphur dioxide, or of hydrogen sulphide, or of other sulphur compounds. Sulphurous acid.

      1. Sulphur dioxide. See under Sulphur. [Obs.]

      2. An acid, H2SO3, not known in the free state except as a solution of sulphur dioxide in water, but forming a well-known series of salts (the sulphites).

         Sulphurous anhydride (Chem.), sulphur dioxide. See under Sulphur.