The Spectrophotometric Determination of Perchlorate Ions by Solvent Extraction with Crystal Violet

Abstract A micro quantity of perchlorate ions is extracted into chlorobenzene with crystal violet. The absorbance maximum of the extract in the organic layer is found to be at 595 mμ. The maximum and the constant extraction was obtained in the pH range of 2–7. In order to ascertain the optimum conditions for the determination of perchlorate ions, various factors have been studied: the effects of the concentration of the dyestuff, the pH of the solution, the standing time of the solution, the times of the extraction, and the presence of diverse ions. The recommended procedure for the calibration curve is as follows: Two milliliters of a crystal violet solution (1×10−3 m), 5 ml of a potassium phosphate buffer solution (1 m, pH 5.8), and various volumes (0–10 ml) of a standard perchlorate solution (2×10−5 mol/l) are mixed. The mixed solution is diluted to 25 ml with water. An aliquot (10 ml) of the solution is then poured into a separatory funnel and is shaken for 5 min with 10 ml of chlorobenzene. The absorbance of the organic layer is measured at 595 mμ against the reagent blank solution. Beer’s law is obeyed in the perchlorate range of 10−7–8×106 mol/l in the aqueous layer before the extraction. Considerable amounts of chloride, iodate, and sulfate ions do not interfere.