Differential Titration of Bases in Glacial Acetic Acid

A study of bases in acetic acid and their differential titration was carried out. The overall basicity constants for 20 bases were measured in acetic acid, and the differential titration of five binary mixtures of variable Δ pKb values in acetic acid was followed using a glass electrode-modified calomel electrode system. Agreement with literature values was good. A leveling diagram was constructed that indicated that bases stronger than aqueous pKb 10 are leveled to an acetous pKb 5.69, whereas weaker bases are not leveled but instead exhibit their own intrinsic basicity, with the acetous pKb to aqueous pKb values being linearly related (slope 1.18, correlation coefficient 0.962). A minimum acetous Δ pKb of four units is required for the satisfactory differential titration of two bases in acetic acid.