Formation constants at high ionic strength-I. Potentiometric determination of protonation constants for succinic, propionic and mono-methyl succinic acid in different ionic media.

The protonation constants, K(r), for the ligands succinic acid (SA), mono-methyl succinate (MS) and propionate (PA) have been determined, at 25 degrees C, by glass electrode potentiometry in 3 mol/dm(3) (M) NaNO(3), KNO(3), NH(4)NO(3), Ca(NO(3))(2) and Et(4)NBr aqueous media. Results are compared with literature constants determined in 3M NaClO(4). The order of stability was found to be K(1)(SA) > K(1)(PA) > K(1)(MS) > K(2)(SA) and for the ligands in the different media K(r) followed the general trend with respect to the background electrolyte Et(4)NBr > NaClO(4) > KNO(3) > NaNO(3) > NH(4)NO(3) > Ca(NO(3))(2).

Formation constants at high ionic strength-II. The ionic strength correction of formation constants using a simplified pitzer equation.

A simplified approach to the correction of equilibrium constants from one ionic strength and/or medium to another is developed. A computer program capable of performing these calculations is presented together with results of its application to the NH (3)H (+), CH (3)COO (-)H (+), CH (3)CH (2)COO (-)H (+), - OOCCH (2)COO (-)H (+) and HOOCCH (2)COO (-)H (+) systems.