EXTRACTION-SPECTROPHOTOMETRIC STUDY ON THE COMPLEX FORMATION IN THE NICKEL (II) - 4-HYDROXY-3-THIOLBENZOIC ACID - DIPHENYLGUANIDINE SYSTEM

The conditions for the complexation of nickel (II) with 4-hydroxy-3-thiolbenzoic acid (HTBA) and diphenylguanidine (DPG) are optimized, such as the formation of the complex in time (8 minutes), pH of the medium (pHop 4.2-5.8), the excess of the reagent, and the conditions for obeying the Bouguer-Lambert-Beer law. The spectral characteristics of the complex (λ= 510 nm) and the HTBA reagent (λ= 195 nm) were studied which showed high sensitivity and contrast (λ= 315 nm) and the true molar coefficient (ε= (3.35× 104) of light absorption was determined. The mole ratio of nickel: reagent is determined by two methods; the equilibrium shift method and the Asmus straight line method, and in both cases the Ni: HTBA: DPG = 1: 2: 2 composition. The interval of obedience to the Bouguer-Lambert-Beer law (0.5-12 μg / 5 ml) and the Sendel sensitivity of 5.34 x 10-3 μg / cm2 are shown. Based on the achieved results and revealed regularities, a photometric technique for determining nickel (II) with HTBA and DPG. Key Words: Nickel (Ii), 4-Hydroxy-3-Thiolbenzoic Acid, Diphenylguanidine, Mixed-Ligand Complexes, Extraction-Photometric Method, Determinatio