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BY-NC-ND 3.0 license Open Access Published by De Gruyter June 2, 2014

Solid-Solute Phase Equilibria in Aqueous Solutions IX. Thermodynamic Analysis of Solubility Measurements: La(OH)m(CO3)q•rH2O

  • Heinz Gamsjäger , Harald Marhold , Erich Königsberger , Yi Jung Tsai and Hans Kolmer

The aqueous solubilities of La(OH)0.8(CO3)1.1.0.1 H2O, basic lanthanum carbonate of ancylite type, have been investigated as a function of ionic strength at 25.0 °C. The stoichiometric solubility constants defined by log* KIps0 = log [La3 +] + 1.1 log pCO2 - 3 log [H+] have the values 11.10, 11.32, 11.42, 11.63, and 11.70 for I = 0.1, 0.25, 1.0, 2.0, and 4.0 mol kg -1(Na)ClO4 respectively. The extrapolation to infinite dilution using the Pitzer equations resulted in a "thermodynamic" solubility constant, log* K°pz0 = 10.48 ± 0.08. This in turn led to the Gibbs energy of ancylite formation: Δf G298 {La(OH)0.8(CO3)1.1 · 0.1 H2O} = - 1.531.5 kJ mol-1.

Received: 1994-10-1
Published Online: 2014-6-2
Published in Print: 1995-1-1

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