Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

m-Aminobenzoic acid displays two protonation equilibria which overlap in the pH region, where pK₂ - pK₁ < 3. The results show that the equilibria occur between the pH values 6.16–1.77, with the limit of separation of the two equilibria lying between 3.60–3.44. Use has been made of several theoretical methods put forward in the bibliography for calculating pK values of overlapping equilibria and these have been corrected by including the terms of the activity coefficients, by means of the coefficients n₁ and n₂, which are defined and calculated by the method of separation of equilibria. The values pK₁ = 3.237 ± 0.091 and pK₂ = 4.767 ± 0.002 are proposed.