SELECTIVE DETERMINATION OF CHROMIUM(VI) BY INDIRECT SPECTROPHOTOMETRY

A simple, and sensitive indirect method for the determination of chrom ium(VI) is described. The method is based on the reduction of chromium (VI) to chromium(III) with excess of thiocyanate ions in the presence of sulphuric acid. The thiocyanate ions, in return, are converted into sulphate and cyanide ions. The surplus thiocyanate is reacted with ir on(III) to give iron(III)-thiocyanate complex. The absorbance of red i ron complex was measured at 450 nm. A linear but inverse calibration w as obtained when chromium(VI) concentration was plotted against the ab sorbance of iron complex. Effect of concerned parameters and possible interferences on the determination have been checked and some syntheti c and real samples of chromium(VI) have been analysed by the described method as well as by a reference spectrophotometric method.