A RIGOROUS SOLUTION TO PROBLEM OF INTERFERING DISSOCIATION STEPS IN TITRATION OF POLYBASIC ACIDS

A general equation for determining thermodynamic proton dissociation constants is described. The treatment is applicable to the simplest case, that of a monobasic acid and to polybasic acids where the successive dissociation steps may or may not interfere. Its versatility is most rewarding in the solution of the problem of overlapping dissociation steps by the analysis of potentiometric data collected from a straight-forward titration of polybasic acids with a strong monoacid base. The interpretation of the general solution is specifically illustrated for citric acid and adipic acid and the results, when compared with published data, are, in both cases, satisfactory. A third example on another acid, whose dissociation constants are not in the literature, illustrates the brief modification required in dealing with an acid salt. © 1969, American Chemical Society. All rights reserved.