Isopiestic Determination of the Osmotic and Activity Coefficients of the {hH2SO4 + (1 − h)Al2(SO4)3}(aq) System at T = 298.15 K. 1. Experimental Results at Stoichiometric Ionic Molality Factions h = (0.85777, 0.71534, 0.57337, 0.42985, 0.28593, and 0.14332)

Isopiestic vapor-pressure measurements have been made at 166 compositions of the {hH2SO4 + (1 − h)Al2(SO4)3}(aq) system at the temperature 298.15 K using H2SO4(aq) as the isopiestic reference standard, where h is the stoichiometric ionic molality fraction of H2SO4 in the mixtures that was calculated by assuming complete dissociation of both solutes. These experiments were performed up to the crystallization limits at values of h = (0.85777, 0.71534, 0.57337, 0.42985, 0.28593, and 0.14332) corresponding approximately to h = (6/7, 5/7, 4/7, 3/7, 2/7 and 1/7); the highest achieved molalities are very slightly above or close to the solubility limits because of the very limited tendency of Al2(SO4)3 to form supersaturated solutions when concentrated isothermally at 298.15 K.