A fast method to determine trace chromium (III) ion in chrome tanning and chrome tanning waste.

Large amounts of chromium (III) ion interfere with the determination of trace amounts of chromium (VI) ion in chrome tanning agents. Therefore, a new method was proposed for determination of trace chromium (III) in chrome tanning products and chrome tanning wastes by automatic reference flow injection. After chromium (III) is oxidised to chromium (VI) by potassium periodate, it can be determined by the flow injection function of an automatic metallic elements analyzer using diphenyl carbazide as the colour developing reagent and potassium periodate as the oxidant solution. The effect of the concentration of potassium periodate and the length of the reaction coil were investigated. Under the optimum conditions, the linear range and RSD of the method were 1.00-100ug/ml and 0.84% respectively. The method was applied to the analysis of chrome powder with recoveries ranging from 95.0% to 103.0%. The results satisfy the requirements of the determination.