1858 Proc. Royal Soc. 9 289 Under the influence of oxide or silver, the bromide yields an alkaline solution possessing all the characters of the -onium-bases.]

1905 Jrnl. Chem. Soc. 88 281 Carbon differs from other elements, which form ‘onium’ bases, in that it forms salts only.

1923 G. N. Lewis Valence ix. 108 The formation of the typical ‘onium’ ion is a process which differs in no essential respect from the other processes in which hydrogen or other radicals become attached to lone pairs.

1953 C. K. Ingold Struct. & Mech. Org. Chem. v. 208 It is not necessary that the anion of the 'onium salt should be the substituting agent.

1991 Progress Polymer Sci. 16 144 Upon irradiation by light, these onium salts generate in situ a strong protonic acid..that initiates cationic polymerization.