Source : Webster's Revised Unabridged Dictionary (1913)

Platinous \Plat"i*nous\, a. (Chem.)
   Of, pertaining to, or containing, platinum; -- used
   specifically to designate those compounds in which the
   element has a lower valence, as contrasted with the platinic
   compounds; as, platinous chloride ({PtCl2}).