Abstract: Blends of crystalline zeolites and sodium triphosphate are made. To this end, a zeolite suspension is spray-dried jointly with an aqueous sodium orthophosphate solution or suspension, in which the molar ratio of Na to P necessary to produce zeolite-free sodium triphosphate containing Na and P in a theoretical ratio of 1.66 is reduced by decrements of 0.01% per each 10% by weight proportion of zeolite in the blend. The zeolite suspension is sprayed separately from the orthophosphate solution or suspension at a separation necessary for the resulting zeolite particles to dry superficially and for the resulting phosphate particles to undergo at least partial condensation, and the superficially dry particles are contacted with the at least partially condensed particles.

Abstract: Polyphosphoric acid is dearsenicated by placing the polyphosphoric acid in a reactor; adding a phosphorus oxo-compound containing phosphorus in the monovalent or trivalent electropositive oxidation stage; heating the resulting mixture to effect disproportionation of the phosphorus oxo-compound; and removing the resulting off-gas having arsenic therein.

Abstract: Waste material consisting substantially of contaminated phosphorous acid is utilized. To this end, the phosphorous acid is introduced, with agitation into a liquid phase. Liquid phase and phosphorous acid are maintained in a ratio by volume between 1:1 and 10:1. The liquid phase is placed in a reactor, maintained between 250.degree. and 400.degree.C and selected from a phosphoric acid of the general formula H.sub.n.sub.+2 P.sub.n O.sub.3n.sub.+1, in which n substantially stands for a number between 1 and 5. Resulting hydrogen phosphide is removed. In the event of continuous operation, newly formed liquid phase is removed from the reactor, at the same rate as it is being formed.