DETERMINATION OF FE(II)-FE(III) AND FE(III)-NI(II) BY THE 2-COMPONENT POTENTIOMETRIC COMPLEXOMETRIC TITRATION

The two-component complexometric potentiometric titration has been applied to the simultaneous determination of Fe(III) and Fe(II), and of Fe(III) and Ni(II) in solution. In each case the two analytes were determined by reading the end-points directly from the titration curve. The end-points are determined in a sense arbitrarily, but they are repeatable and easy to be detected precisely. However, the apparent (found) analytical results are biased. They are effectively corrected with the use of a set of two calibration equations (incomplete second degree polynomials), which approximate the relationship between found end-points and true concentrations of analytes in solution. The regression, coefficients in the equations are determined on the basis of titration data obtained for standard solutions whose compositions correspond to a 2(2) factorial.