Spectrophotometric determination of the acid dissociation constants of 3-hydroxypyridine

The graphic method of Alberty and Massey was adapted to the determination of the acid dissociation constants of dibasic acids. When the absorbancy at a particular wavelength is plotted as a function of pH, a symmetrical bell-shaped curve may be observed. The pH values at the half-absorbancy points and at the maximum of the curve provide sufficient information to calculate the p K values. The procedure was applied to the determination of the ionization constants of 3-hydroxypyridine.