“…-naphthylamine and cumidine (23), tetramethyl-p-diaminodiphenylmethane (10,20), 1,4-diphenylendanilodihydrotriazole (Nitron) (4), quinoline (15), tannin (16,21), phenylhydrazine hydrochloride (2), 8-hydroxy quinoline (5,9,18), vanillylidene-benzidine (7), and rhodamine B (17). None of these reagents has proved sufficiently effective to replace cinchonine as the preferred reagent in standard procedure, although its use involves certain difficulties (1,6,12).…”