Osmotic Coefficients of Two Amino Acid Magnesium Salts at 298.15 and 310.15 K

The concentration dependence of the vapor pressures of magnesium l-glutamate and magnesium l-aspartate solutions has been studied with the help of vapor pressure osmometry measurements, performed as a function of salt concentration in the range m (i) = 0.01-0.43 and m (i) = 0.01-0.30 mol center dot kg(-1), respectively, at T = 298.15 and 310.15 K. From these experimental results, the activities of water and the corresponding osmotic coefficients have been calculated for all systems investigated. Mean molal ion activity coefficients were obtained from experimental data fits with the Pitzer equations and the corresponding dual and triple interaction parameters were derived. beta ((2)) Pitzer parameters different from zero are required where the osmotic coefficient decreases strongly with increasing concentration at 298.15 and 310.15 K. beta ((1)) and beta ((2)) analysis shows that the interaction nature is different for magnesium aspartate and magnesium glutamate solutions (the ratio of repulsion/attraction parts is different). The decrease in the chemical potential of the glutamates corresponds to the Hofmeister series: KGlu > NaGlu > Mg(Glu)(2) > Ca(Glu)(2).