Stannous \Stan"nous\ (-n[u^]s), a. (Chem.) Pertaining to, or containing, tin; specifically, designating those compounds in which the element has a lower valence as contrasted with stannic compounds.

Stannous chloride (Chem.), a white crystalline substance, SnCl2.(H2O)2, obtained by dissolving tin in hydrochloric acid. It is used as a mordant in dyeing.

Source: Webster's Revised Unabridged Dictionary (1913)