Direct spectrophotometric determination of rare earths in organic extracts with chlorophosphonazo III

The highly sensitive spectrophotometric determination of rare earths after extraction into di(2-ethylhexyl)phosphoric acid and trioctylamine is described. A sample of extract is diluted with n-butanol, the solution of chlorophosphonazo III in n-butanol is added, and the solution is made up to defined volume. Absorbance is measured at 660–665 nm against a reagent blank. The method is suitable for the study of the extraction of individual rare earths by different organic extrahents.