Spectrophotometric analysis of simultaneous protolysis equilibria.
Simultaneous protolysis equilibria can be spectrophotometrically analysed easily by means of absorbance diagrams. The dissociation constants K(1) and K(2) can be determined directly from distinct points on the absorbance diagram by correlation with a photometric titration plot of absorbance vs. pH. Furthermore, from the absorbance diagram the ratio K (2)K (1) can be evaluated from the ratio of corresponding sides, and pH-measurement is not necessary. The titration systems of a mixture of 2-nitroso-l-naphthol-4-sulphonic acid with P-nitrophenol, and a mixture of P-nitrophenol with o-nitrophenol have been analysed by these methods, and are described as examples.
Polster
J
J
Lehrstuhl Für Allgemeine Chemie und Biochemie Der Technischen Universität München, D-8050 Freising-Weihenstephan, BRD.