Gravimetric analysis of tantalocolumbites by precipitation from homogeneous solution

An analysis of complex tantalocolumbites has been carried out by precipitation from homogeneous solutions. A homogeneous precipitation of tungsten, titanium, tantalum and niobium by thermal decomposition of the soluble peroxytungstates, described in previous papers, is used. Corrections for incomplete precipitation and coprecipitation phenomena are applied on the basis of the experimentally found values. Silicon and tin are separated by volatilisation as fluoride and iodide, respectively. Iron is extracted by means of isopropyl ether and the rare earth metals are precipitated homogeneously from an oxalate solution. Manganese is precipitated as the ammonium phosphate. The results are in good agreement with an independent method, the standard deviations being within 1 % for the major constituents.