The reaction between 2 acetamino 6 amino benzo thiazole and chloroiridio acid is not sensitive enough to be of importance as a colorimetric quantitative reaction. IrCl₆-- can be detected with this organic compound if iridium is present in as much as 0.02 mg. per ml. of solution providing ferric iron is absent. If ruthenium is present it must be removed before the test for the iridium anion can be made. / M.S.