Phosphate can be rapidly and easily titrated thermometrically using a standard solution of Mg²⁺ as titrant. The phosphate-containing solution is basified and buffered with NH₃/NH₄Cl solution before titration. The formation of insoluble MgNH₄PO₄ is exothermic. The method is a titrimetric adaptation of a classical gravimetric procedure.

This bulletin deals with the determination of phosphate in phosphoric acid and granular fertilizers such as MAP (monoammonium phosphate), DAP (diammonium phosphate) and TSP (triple superphosphate). Results are reported as percentage of P and P₂O₅.

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