Solubility Products of Calcium Isosaccharinate and Calcium Gluconate.

Evaluation of equilibrium constants for deprotonation and lactonisation of α-D-isosaccharinic acid

“…Lines represent predicted concentrations: heavy solid lines represent total concentrations of either Ca or ISA and other lines concentrations of different species as marked. −3.27 ± 0.01 and 0.49 ± 0.09, respectively, and these values are (1) consistent with the extensive Ca-ISA system data reported by several authors [5,[21][22][23]27,28] and Hummel et al's [10] recommended values based on their critical review of these data using the SIT model, and (2) similar to the values Rai et al [5] determined based on the interpretation of Ca-ISA system data using the Pitzer model. The average values for the solubility product for Ca(ISA) 2 (cr) and formation of CaISA + recommended by Hummel et al [10] have been verified in this study.…”

“…The ideal solubility study for this purpose must have the following attributes: (1) the solid phase used should be crystalline, rather than amorphous, 3 with rapid precipitation/dissolution kinetics, (2) the study should be conducted in the acidic region (pH < 5) with several data points per pH unit, (3) the cation of the solid phase should not: (a) make strong complexes with ISA − or if it does then the reliable complexation constant values should be available, and (b) form strong complexes with hydroxide in the low pH region, and (4) the equilibration period should be relatively long. Among the solid phases (ThO 2 (am), NpO 2 (am), PuO 2 (am), Fe(OH) 3 (am), and Ca(ISA) 2 [3,5,6,9,[20][21][22] for which solubility data in the presence of ISA are available, the only ones that meet all of the above criteria for ideal solubility study are the Ca(ISA) 2 (cr) studies by Rai et al [5,23].…”

“…As discussed earlier, extensive Ca(ISA) 2 (cr) solubility data-sets [5,21], 6 (I) as a function of pH (varying from 2.61 to 10.87), (II) at a fixed CaCl 2 concentration of 0.036 mol kg −1 and as a function of pH (varying from 2.88 to 10.96), (III) at a fixed pH value of approximately 8.0 and as a function of CaCl 2 molality (varying from 0.03 to 0.26), and (IV) at a fixed pH value of approximately 8.2 and as a function of isosaccharinate molality (varying from 0.02 to 0.20), can be interpreted, especially the low pH data, in combination with HISA(aq) deprotonation constant selected above to obtain a reliable value for the lactonisation constant. Data-sets I-III are from Rai et al [23] and data-set IV is from Rai et al [5].…”

Dissociation Constants of α-d-Isosaccharinic Acid: “Composite” and “Intrinsic” Values

“…Instead, dissolution of Ca(ISA) 2 (s) to Ca 2+ and ISA -was proposed, with the reinterpreted solubility constant being consistent with other data in the literature. 20,21 As a consequence, the validity of the ISA dissociation constant obtained in the earlier work is questionable. This conclusion was also reached by Hummel et al 8 in their review of ISA complexation.…”

The effect of α-isosaccharinic acid on the stability of and Th(IV) uptake by hardened cement paste

“…Based on the above assumptions, it was estimated that the aqueous ISA concentration was allowed to be at most 10 −3 M at a S/L ratio of 10 −4 kg L −1 and at most 5 × 10 −2 M at a S/L ratio of 5 × 10 −3 kg L −1 . Note that the maximum ISA concentration in the cement pore water at pH 13.3 was determined to be 4.4 × 10 −2 M [24]. Based on these findings, maximum ISA concentrations have been considered in the uptake experiments according to the S/L ratios and the free ISA concentrations of the suspensions.…”