We don't have synonyms for selenous yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are selenium, seleucus and selenious.
(adj) :
Alternative form of selenious. [(inorganic chemistry) Of, pertaining to, or containing selenium, especially in a lower oxidation state than corresponding selenic compounds.]
(adj) :
Alternative form of selenious. [(inorganic chemistry) Of, pertaining to, or containing selenium, especially in a lower oxidation state than corresponding selenic compounds.]