noun
also thio·glycollic acid |thīō+...-
Etymology: thioglycolic, thioglycollic International Scientific Vocabulary thi- + glycolic, glycollic (in glycolic acid, glycollic acid )
: an ill-smelling liquid mercapto acid HSCH 2 COOH analogous to the hydroxy acid glycolic acid that is made usually by reaction of chloroacetic acid and hydrogen sulfide, that is a sensitive reagent for ferric iron (as by the formation of an intense red color in ammoniacal solution), and that is used chiefly in the form of its ammonium salt in setting cold waves and in the form of the calcium and other alkaline salts as depilating agents — called also mercaptoacetic acid ; not used systematically