pH-static techniques in volumetric analysis I. A theoretical reappraisal of pH-static acid-base Titrations

摘要

The pH-static option available in many potentiometric titrators can be exploited for acid-base titrations. The procedure consists of continuous or stepwise addition of the titrand solution to a suitable supporting solution (containing an inert electrolyte and, if necessary, a small concentration of buffer), and simultaneous addition of titrant to keep the measured pH at an appropriate constant value. Titrations of moderately concentrated strong and weak acids and bases are theoretically investigated. The criteria of choice of the experimental parameters, particularly of operating pH, ionic strength and buffer power of the measured solution, are discussed. The way these parameters affect the accuracy and the precision of the results is examined. It is inferred that pH-static titrations can be competitive with traditional titration procedures, particularly for the determination of the effective strength of secondary standard solutions of strong bases. Moreover, they can be used straightforwardly for the determination of acidity constants. [References: 22]