Solubility of crystalline calcium isosaccharinate

The solubility of calcium isosaccharinate Ca(ISA)(2)(c) was determined at 2 3 degrees C as a function of pH (I - 14) and calcium ion molality (0.03-0.5 2). The similarity of solubility from the over- and undersaturation directi ons for different equilibration periods indicated that equilibrium in these solutions was reached rapidly (< 7 days) and that these data can be used t o develop thermodynamic equilibrium constants. The solubility data were int erpreted using the Fitter ion-interaction model. The logarithms of the ther modynamic equilibrium constants determined from these data were 1.30 for th e dominant reaction at pH < 4.5 [Ca(ISA)(2)(c) + 2H(+) reversible arrow Ca2 + + 2HISA(aq)], and -2.22 for the dominant reaction at pH > 4.5 [Ca(ISA)(2) (c) reversible arrow Ca(ISA)(2)(aq)]. In addition, the logarithm of the dis sociation constant of HISA [HISA(aq) reversible arrow ISA(-) + H+] was calc ulated to be -4.46.