althionic,a.Chem.|ælθɪˈɒnɪk| [f. alcohol) + Gr. θεῖον sulphur + -ic.] In althionic acid, C2H4SO4, produced, according to Regnault, by heating alcohol with an excess of strong sulphuric acid. 1858in Penny Cycl. 2nd Supp. 126/2. 1863 Watts Dict.Chem. I. 149 The barium-salt of althionic acid.