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Complexation of Calcium by alpha-Isosaccharinic Acid under Alkaline Conditions.

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43

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0

References

1999

Year

Karlien Vercammen, Martin A. Glaus, Luc R. Van Loon, Saktiprosad Ghosh, Pher G. Andersson, Jørgen Møller, Alexander Senning, Xin‐Kan Yao, Honggen Wang, J.-P. Tuchagues,
Acta chemica Scandinavica/Acta chemica Scandinavica. B, Organic chemistry and biochemistry/Acta chemica Scandinavica. A, Physical and inorganic chemistry/Acta chemica Scandinavica. Series B. Organic chemistry and biochemistry/Acta chemica Scandinavica. Series A, Physical and inorganic chemistry

Abstract

The complexation of Ca<sup>2+</sup> by α-isosaccharinic acid (α-ISA) was determined by measuring the solubility of Ca(α-ISA)<sub>2</sub> as a function of pH. In the pH range between 12 and 12.8, the observed increase of the total concentration of Ca in solution with increasing pH is explained by the complexation reaction:<br /><br /> Ca<sup>2+</sup> + α-ISA<sup>–</sup> ⇋ Ca(α-ISA<sub>–H</sub>)<sup>0</sup> + H<sup>+</sup><br /><br /> with log <em>K</em>°<sub>CaISA<sup>0</sup></sub> = –10.4 (<em>s</em> = 0.2) at I = 0. In addition to this complexation reaction, another complex is postulated:<br /><br /> Ca<sup>2+</sup> + α-ISA<sup>–</sup> ⇋ Ca(α-ISA)<sup>+</sup><br /><br /> with log <em>K</em>°<sub>CaISA</sub><sup><sub>+</sub></sup>= 1.70. A value for the solubility product of Ca(α-ISA)<sub>2</sub> is calculated: log K°<sub>sol</sub> = –6.36 (<em>s</em> = 0.1) at <em>I</em> = 0.