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This article in SSSAJ

  1. Vol. 52 No. 6, p. 1566-1570
    Received: Jan 25, 1988

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Solubility of Barium Arsenate

  1. M. E. Essington 
  1. Division of Waste Characterization and Chemistry, Western Res. Inst., Univ. of Wyoming Res. Corp., P.O. Box 3395, Laramie, WY 82071



Current thermodynamic data suggest barium arsenate [Ba3(AsO4)2(c)] to be a highly stable phase. However, sufficient evidence is available to question the validity of the current data. In order to determine the solubility (pKsp) and calculate the standard free energy of formation (Δf) of Ba3(AsO4)2(c), an equilbrium solubility study was conducted. The equilibrium experiments were carried out under three different ionic strength conditions for reaction times up to 45 d. Equilibrium was approached from both undersaturated and supersaturated initial conditions. The pKsp for the dissolution of Ba3(AsO4)2(c) was calculated to be 21.62. Correspondingly, a Δf of − 3101.2 ± 2.0 kJ mol−1 was calculated. This value is 166.9 kJ mol−1 more positive than the current literature value. Reevaluation of the solubility data from a previous work suggests that the pKsp for the dissolution of BaHAsO4 · H2O(c) is 24.64 and the corresponding Δf is − 1587.0 ± 2.5 kJ mol−1.

Contribution of the Division of Waste Characterization and Chemistry. Support by the U.S. Dep. of Energy, as part of Cooperative Agreement no. DE-FC21-86MC11076, is gratefully acknowledged.

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