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This article in SSSAJ

  1. Vol. 24 No. 2, p. 94-98
    Received: Aug 24, 1959
    Accepted: Dec 21, 1959

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Solubility of Dicalcium Phosphate Dihydrate in Aqueous Systems1

  1. Edgard C. Moreno,
  2. Walter E. Brown and
  3. Glen Osborn2



The metastable solubility isotherm for dicalcium phosphate dihydrate, CaHPO4·2H2O, (DCPD), in the pH range 3.5 to 7.5 was established by (a) leaching solutions of dilute phosphoric acid through columns of DCPD, and (b) by shaking suspensions of DCPD in dilute phosphoric acid solutions.

In other experiments, equilibrium was approached both from undersaturated and supersaturated conditions. In both cases the final solution compositions were represented by points on the isotherm obtained by the methods mentioned above, and dissolution or precipitation occurred with a Ca/P ratio equal to one.

The solubility product constant of DCPD was found to be 2.77 × 10-7 for all concentrations tested when appropriate corrections were made in the calculation of ionic activities.

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