[Solubility and the complex-forming properties of the zwitterlytes, 6-aminopenicillanic and 7-aminodesacetoxycephalosporanic acids].

Relation between solubility of the zwitterlites 6-aminopenicillanic acid (6-APA) and 7-aminodesacetoxycephalosporamic acid (7-ADCA) and the ionic strength and pH of the solution was studied. A specific effect of benzylpenicillin (BP) and 7-phenylacetamidodesacetoxycephalosporanic acid (7-PADCA) on solubility of the above zwitterlites was found and complex formation was suggested. An explanation of the complex formation mechanism and a method for estimation of the instability constants of the complexes are presented. The method is based on determination of the changes in the zwitterlite solubility in the presence of the complex forming compound. The values of the characteristic solubility of the ampholyte zwitter ions and the instability constants of the complexes "zwitterlite-complex forming compounds" were determined. A mathematical description of the relation between the zwitterlite solubility within a wide range of pH and concentrations of the complex forming compounds is presented. Coincidence of the calculated and experimental data was observed, which provided a supposition that the substances involved in complex formation were charged.