The Collaborative International Dictionary of English v.0.48:
Mercurous \Mer*cu"rous\, a. (Chem.) Of, pertaining to, or derived from, mercury; containing mercury; -- said of those compounds of mercury in which it is present in its highest proportion. [1913 Webster] Mercurous chloride. (Chem.) See Calomel. [1913 Webster]WordNet (r) 3.0 (2006):
mercurous adj 1: of or containing mercury [syn: mercuric, mercurous]