1987 Volume 51 Issue 12 Pages 1159-1165
The present investigation was carried out to examine the chemical composition of precipitates produced during a titration of aqueous solution containing gallium sulfate with sodium hydroxide, to obtain the standard free energy of formation of Ga(III)-hydroxysalt, and to determine the pH-dependence of its solubility at 333 K.
The results obtained are summarized as follows:
(1) The hydrolysis proceeds via two steps. The precipitates produced in the first and second steps of hydrolysis were identified to be {Nax, (H3O)1−x}Ga3(SO4)2(OH)6, where the value of x varies with the composition of the solution, and GaOOH, respectively. These Hydrolysis reactions are represented by xNa++3Ga3++αSO42−+βHSO4−+(7−x)H2O={Nax,(H3O)1−x}Ga3(SO4)2(OH)6+(5+x+β)H+, where α+β=2, and {Nax,(H3O)1−x}Ga3(SO4)2(OH)6+(x−1)H2O=3GaOOH+(x⁄2)Na2SO4+((4−x)⁄2)H2SO4.
(2) The standard free energy of formation of {Nax, (H3O)1−x}Ga3(SO4)2(OH)6 was obtained for the values of x=0.13, 0.22, 0.38, and 0.66 at 333 K.
(3) The pH-dependence of the solubility of {Nax, (H3O)1−x}Ga3(SO4)2(OH)6 was determined for various choices of the parameter, which can be calculated from the initial composition of solutions.
