Abstract
Colorimetric determination of cadmium using 2, 2'-bisbenzothiazoline has been studied.
Cadmium formed a red-violet complex with the reagent in a highly basic aqueous solution, and the complex was extracted into chloroform-pyridine (4+1) mixture.
The complex in the organic solvent showed two characteristic absorption maxima, one at 370 mμ and the other at 570 mμ. The color in the organic solvent was stable for 25 minutes. The calibration curve followed Beer's law over the range of 4120 μg of cadmium in 10 ml of the solvent (both at 370 mμ and at 570 mμ). The molar extinction coefficients were 3800 at 570 mμ and 10000 at 370 mμ.
Nickel, cobalt, copper, zinc, manganese, lead, iron, silver, mercury and magnesium interfered, but their permissible amounts were increased by addition of masking agents.
The proposed method was applied to the determination of cadmium in zinc metal with good results.
