The Collaborative International Dictionary of English v.0.48:
Argentous \Ar*gen"tous\, a. (Chem.) Of, pertaining to, or containing, silver; -- said of certain silver compounds in which silver has a higher proportion than in argentic compounds; as, argentous chloride. [1913 Webster]WordNet (r) 3.0 (2006):
argentous adj 1: relating to compounds in which silver is univalent