Complex formation of acetic acid with Ca(II) and Mg(II) under physiological conditions

Potentiometric titrations of aqueous acetic acid alone and in the presence of Ca(II) or Mg(II) ions have been carried out under physiological conditions at the temperature 37 degrees C and ionic strength 0.15 mol center dot dm(3)supercript stop (NaCl) at different ligand-to-metal ratios. Changes in pH were monitored with a glass electrode calibrated daily in terms of the hydrogen ion concentrations. Titration data within the pH range 2.5 to 6.6 were analyzed to determine stability constants using the SUPERQUAD program. Different combinations of complexes were considered during the calculation procedure for both systems, but evidence was found only for mononuclear ML and ML2 species. Speciation calculations based on the corresponding constants were then used to simulate the species' distributions.