Solubility of (NH4)Al(SO4)(2)center dot 12H(2)O in the systems H2O-(NH4)Al(SO4)(2)-H2SO4 and H2O-(NH4)Al(SO4)(2)-H3PO4 at the temperatures of 20 degrees C and 30 degrees C and vapour pressure above these systems

Influence of concentration of H2SO4 and H3PO4 On the solubility of (NH4)Al(SO4)(2) . 12H(2)O in aqueous solutions and vapour pressure above saturated solutions of the systems H2O-(NH4)Al(SO4)(2)-H2SO4 and H2O-(NH4)Al(SO4)(2)-H3PO4 was investigated. The measurements were carried out at the temperatures of 20 degrees C and 30 degrees C. It is shown that in the system H2O-(NH4)Al(SO4)(2)-H2SO4 solubility of (NH4)Al(SO4)(2) . 12H(2)O increases with increasing concentration of H2SO4 up to 8 mass % H2SO4. When concentration of the acid further increases, solubility of (NH4)Al(SO4)(2) . 12H(2)O decreases. However, from the concentration of ca. 35 mass % H2SO4 it starts to increase again. At high concentrations of sulfuric acid (> 30 mass %) it is Al-2(SO4)(3) . 16H(2)O and not (NH4)Al(SO4)(2) . 12H(2)O which is in equilibrium with the solution. Water vapour pressure above the solutions shows how the activity of water changes with composition of the investigated systems.