Dependence on Ionic Strength of Formation Constants, Protonation, and Complexation of Nitrilotriacetic Acid with Tungsten(VI) in Sodium Perchlorate Aqueous Solution

Abstract

By use of potentiometric and spectrophotometric techniques, the complexation of tungsten(VI) with nitrilotriacetic acid (NTA) has been carried out in aqueous solution for pH = 7.5 at 25 °C and different ionic strengths ranging from (0.1 to 1.0) mol dm -3 (NaClO 4 ). The composition of the complex was determined by the continuous variations method. It was shown that tungsten(VI) forms a mononuclear complex with NTA of the type (WO 3 L 3- ) at pH = 7.5. The dependence of the protonation of the aforementioned ligand and the stability constant of the complex on ionic strength is described by a Debye−Huckel-type equation. Finally the results have been compared with the previously reported data.