SPECTROPHOTOMETRIC DETERMINATION OF MOLYBDENUM AND TUNGSTEN IN THE SOIL OF THE JABRAYIL REGION WITH 2-HYDROXY-5-HALIGENTHIOPHENOLS AND AROMATIC AMINES

Abstract

In the interaction of molybdenum and tungsten with 2-hydroxy-5-halogenthiophenols, mixed-ligand complexes (MLC) extractable with chloroform are formed. Aniline, N-methylaniline, and N, N-dimethylaniline were used as the hydrophobic amines. The conditions for the extraction-photometric determination of molybdenum and tungsten are found. The best extractants were chloroform, dichloroethane and carbon tetrachloride. In a single extraction with chloroform, 97.8–98.2% of molybdenum and tungsten are recovered in the form of MLC (in the case of C2H4Cl2 and CCl4, 95–96% of molybdenum and tungsten are recovered). Molybdenum and tungsten MLC extracts obey the basic law of light absorption at concentrations of 0.2–20 and 0.2–19 μg/mL, respectively. It was established by the Nazarenko method that the complexing form of molybdenum and tungsten is MeO (OH)2+. It was found that MLC are formed at pHopt. 1.8-5.1. The maximum in the light absorption spectrum is observed at 457–538 nm. The molar light absorption coefficient is (3.2-4.2) ×104. It has been proven that molybdenum (VI) and tungsten (VI) are reduced to Me(V) by the reagent itself upon formation of a complex with halothiophenols. Keywords: molybdenum, tungsten, 2-hydroxy-5-halogenthiophenol, extraction-photometric method, hydrophobic amines