It has been found that both 2, 6-and 2, 7-di-t-butylnaphthalene form the same disulphonic acid when treated with 2 molar equivalents of chlorosulphonic acid. It is suggested that this acid is 2, 6-di-t-butylnaphthalene-4, 8-disulphonic acid. The evidence, including the nmr spectrum, on which the proposed structure is based is presented.