SPECTROPHOTOMETRIC DETERMINATION OF TOTAL RARE-EARTHS IN MINERALS WITH THE CHROMOGENIC REAGENT PARA-ACETYLCHLOROPHOSPHONAZO

The synthesis and purification of p-acetylchlorophosphonazo (CPApA) are described. A method is proposed for the spectrophotometric determination of total rare earths with CPApA in 0.2 M hydrochloric acid medium at their isosbestic point (667 nm). At this wavelength, the absorbances of equal amounts of rare earths are very close to each other. Beer's law is obeyed for 0-12-mu-g of rare earths in 25 ml of solution. The method has been satisfactorily applied to the determination of total rare earths in minerals with a prior organic extraction.