Separation of thorium from trivalent rare earths in monazite and its gravimetric determination using o-carboxyphenylazo-β-naphthol

In the present work, the use o-carboxyphenylazo-β-naphthol (CPAN) in quantitatively precipitating thorium in the presence of ten-fold excess of lanthanum in a single precipitation at pH 5.3 is reported. Since in Indian monazite, the ratio of ThO2 to R2O3 is 1:8, the advantage offered by this reagent in the recovery of thorium from monazite becomes more apparent. (author)