The detection of cadmium with the aid of Cadion 2B as proposed by Dwyer has been applied to the colorimetric determination of cadmium.The colored suspension formed is unstable, but it can be stabilized by addition of 1% gelatin solution.The conditions of determination have been investigated with a spectrophotometer(Unicam SP.500) and are summarized briefly as follows:1.The reagent Cadion 2B has a maximum absorption at 590 mμ; in presence of an excess of cadmium the maximum shifts to 510 mμ.