INFLUENCE OF HYDROXYCARBOXYLIC ACIDS ON THE WATER SOLUBILITY OF VARIOUS BISMUTH COMPOUNDS

In an equilibrium dialysis assay (bismuth being determined by atomic a bsorption spectrometry) a constant amount of bismuth (Bi, CAS 7440-69- 9) (final maximum conc. 50 mu mol/l Bi/l) was dialyzed against solutio ns with increasing concentrations of the chelators (0-25 mmol/l). At p H 5, 50% of Bi(III) nitrate was soluble in solutions with 0.3, 6.3, 13 .4 and 14.6 mmol/l of edetic acid (EDTA), citric tartaric and malic ac id, respectively. At the highest concentration applied, lactic acid ke pt 7% of bismuth in solution. Without any chelator, bismuth was found to be essentially insoluble (limit of detection: approx. 4 nmol Bi/l). A concentration-dependent increase in solubility was found also for t he other bismuth compounds; the sequence of the solubilizing capacity of the chelators was the same as for Bi(III) nitrate. Lowering the pH to 3 generally increased and raising the pH to 7, decreased the solubi lity of bismuth.