Abstract
A spectrophotometric investigation was made on the complexes formed between 1-(2-pyridylazo)-2-naphthol(PAN) and zinc(II) in 20vol% dioxane solution. As to their complex compositions, it was found that the molar ratio of zinc(II) and PAN was 1 : 1 and 1 : 2 in the solution of pH 4?6, while molar absorption coefficient was 2.5 × 104 at 540 mμ.
The equilibrium constant for the reaction, HA + Zn(II)_??_ZnA++H+, was 2.5 × 10-2 and the stability constant for the complex(1 : 1) was approximately 4.0 × 1010. The theoretical error in the titration of zinc(II) with ethylenediaminetetraacetic acid(EDTA) using PAN as an indicator was calculated from the stability constant of the complex obtained, and the optimum pH range for the titration was discussed.
