Concd. soins. of P(2)O(5) (51-61%) were neutralized with a mixt. of CaO and CaCO(3) to CaHPO(4), After the product was sepd. by crystn. and dried at 150 degrees C for 30-40 min, the water content decreased down to below 2%. The content of H(2)O-sol. P(2)O(5) in the product was 42.7-52.8%. The drying kinetics was correlated by a polynomial equation.