The Collaborative International Dictionary of English v.0.48:

Palladious \Pal*la"di*ous\ (p[a^]l*l[=a]"d[i^]*[u^]s), a.
   (Chem.)
   Of, pertaining to, or containing, palladium; -- used
   specifically to designate those compounds in which palladium
   has a lower valence as compared with palladic compounds.
   [1913 Webster]