SULPHONIC

Adjective

sulphonic (not comparable)

Alternative spelling of sulfonic

Source: Wiktionary

Sul*phon"ic, a. (Chem.)

Definition: Pertaining to, or derived from, a sulphone; -- used specifically to designate any one of a series of acids (regarded as acid ethereal salts of sulphurous acid) obtained by the oxidation of the mercaptans, or by treating sulphuric acid with certain aromatic bases (as benzene); as, phenyl sulphonic acid, C6H5.SO2.OH, a stable colorless crystalline substance. Sulphonic group (Chem.), the hypothetical radical, SO2.OH, the characteristic residue of sulphonic acids.

Source: Webster’s Unabridged Dictionary 1913 Edition