The catenation and isomerisation effects on stability constants of complexes formed by some diprotic acids

Stability constants (Kijk) of complexes NaiKjHkL+i+j+k−2 (0<i+j+k≤2) formed by dicarboxylic (oxalic, malonic, succinic, glutaric, adipic and methylmalonic, dimethylmalonic, ethylmalonic) acids in solutions of mixed salts (NaNO3, KNO3) of ionic strength I=1.64 mol l−1 are presented. The unbiased values for Kijk, (Kijk)% e=0, were obtained from the linear relationships log Kijk=a+b(% e) stated on the basis of the results of repeated titrations made in titrand+titrant systems of high ionic strength, % e is the relative error of determination of the weak acid (H2L) concentration. These data were then applied to indicate the catenation or the isomerisation effects on the Kijk values.