sulphurous, a. [L. sulphurosus, sulfurosus: cf. F. sulfureux.].
Sulphurous acid. (a) Sulphur dioxide. See under Sulphur. [Obs.] (b) 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.
Of or pertaining to sulphur. [1913 Webster]
Derived from, or containing, sulphur; specifically, designating those compounds in which the element has a lower valence as contrasted with the sulphuric compounds. [1913 Webster]