Production of alkali metal phosphate solutions of low vanadium content

In a process for making alkali phosphate solutions of low vanadium content from wet-processed phosphoric acids contaminated with vanadium and iron, wherein the acids containing vanadium and iron in the highest stage of oxidation are treated with a reductant to effect conversion of the vanadium and iron comtaminants to a lower stage of oxidation, the resulting acids are neutralized by means of an alkaline liquor or alkali metal carbonate or mixture thereof down to a pH of a least 3, and the resulting precipitate is separated, the improvement which comprises using the sodium salt of hydroxymethanesulfinic acid as the reductant.