Indirect spectrophotometric determination of perchlorate using nitron as reagent

An indirect method is outlined for the spectrophotometric determination of small amounts of perchlorate. Perchlorate is quantitatively precipitated as nitron perchlorate in the presence of excess nitron. After separating off the precipitate, the excess reagent is determined in the supernatant liquid as nitron cobaltothiocyanate. The latter compound is extracted in 30% cyclohexanone in carbon tetrachloride and the absorbance of the extract measured at 625 nm. The method is simple, reproducible, and accurate to ±1%. The interferences of other anions were also investigated.