End-point construction and systematic titration error in linear titration curves-complexation reactions

Abstract

The systematic titration error which is introduced by the intersection of tangents to hyperbolic titration curves is discussed. The effects of the apparent (conditional) formation constant, of the concentration of the unknown component and of the ranges used for the end-point construction are considered. A graphical method is presented for the selection of pairs of ranges which result in small systematic titration errors. The method permits the selection of pairs of ranges with equal or unequal intervals before and after the end-point. For titration curves with a reversed-L shape, the error is calculated when the end-point is constructed by the intersection of the tangent to the second branch of the curve with the volume axis. The systematic titration error is equal to - 1/Kcx when the tangent to the curve is taken at fu=3.0.