Solid-solute phase equilibria in aqueous solutions, VIII: The standard gibbs energy of La2(CO3)3·8H2O

摘要: The solubilities of lanthanum carbonate La2(CO3)3·8H2O in solutionsS 0([H+]=H mol kg−1, [Na+]=(I−H) [ClO 4 − ]=I kg−1) at various fixed partial pressures CO2 have been investigated 25.0 °C. hydrogen ion molality and the total La(III) equilibrium with solid phase were determined by e.m.f. analytical methods, respectively. stoichiometric solubility constants $$\log ^ \star K_{ps0}^I = \log \{ [La^{3 + } ]p_{CO_2 }^{3/2} [H^ ]^{ - 3} \}$$ according to overall reaction $$1/2La_2 (CO_3 )_3 \cdot 8H_2 O 3H^ \rightleftharpoons La^{3 3/2CO_2 11/2H_2 O$$ values 10.23, 10.37, 10.58, 10.77 11.06 forI=0.1, 0.25, 1.0, 2.0 4.0 kg−1 (Na)ClO4, extrapolation infinite dilution using Pitzer equations resulted a “thermodynamic” constant: K_{ps0}^0 ([La^{3 )(\gamma _{La^3 \gamma _{H^ }^{ )a_{H_2 O}^{11/2} \} 9.57 \pm 0.05$$ . This turn led Gibbs energy lanthanite, La2(CO3)3·8H2O, formation: $$\Delta _f G_{298}^{O 5048.4 kJ mol^{ 1}$$