arsonium Chem.
(ɑːˈsəʊnɪəm)
[f. ars-enic + termination of ammonium.]
A name applied (chiefly in combination) to a univalent organic arsenic radical, analogous in composition to ammonium and phosphonium, as tetramethyl-arsonium As(CH3)4. Hence arsonic (ɑːˈsɒnɪk), a., pertaining to arsonium; applied to a group of acids, analogous to the phosphonic acids (Fownes).