Gravimetric determination of tungsten by homogeneous precipitation

Abstract

A homogeneous precipitation method has been developed for the gravimetric determination of tungsten, by thermal decomposition of soluble peroxytungstate from a nitric acid-hydrogen peroxide solution. It appears that in all cases, especially for small concentrations, the tungsten recovery is superior to the classical techniques using cinchonine or β-naphthoquinoline. Furthermore, co-precipitation of molybdenum and vanadium are reduced to a considerable extent. The study of the co-precipitation process shows that the distribution coefficients follow a linear pattern for both contaminants. The method has been tested with good results on a number of standard tungsten alloy steels, corrections for incomplete precipitation and co-precipitation being applied on the basis of the experimentally found values.