[01] Ali Z. Zalov, Department of Analytical Chemistry, Azerbaijan State Pedagogical University, Baku, Azerbaijan. [02] Kiril B. Gavazov, Department of General and Inorganic Chemistry, University of Plovdiv “Paissii Hilendarski”, Plovdiv, Bulgaria.

29 liquid-liquid extraction-chromogenic systems containing MV (M=Nb or Ta), thiocatecholic compounds (TCs) and hydrophobic amines (HAs) were studied. The following TCs were used: 2,4-dihydroxythiophenol (DHTP), 2-hydroxythiophenol (HTP), 2-hydroxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP), and 2-hydroxy-5-iodothiophenol (HBIP). The HAs were aniline (An), N-methylaniline (MAn), N,N-dimethylaniline (DAn), aminopyridine (APy), dipyridyl (DiPy), guanidine (Gu), diphenylguanidine (DPG), and triphenylguanidine (TPG). The best organic solvent was chloroform. Under the optimum conditions, the molar absorptivities (εmax) and the degrees of MV extraction (R%) in this solvent were in the ranges (1.6-3.9)×104 L mol-1cm-1 and (98.1-99.3)%, respectively. The molar ratio of the reacting species was 1:2:2 (MV:TC:HA). Relationships were studied between the acid-base properties of the sulfhydryl group of TCs (pKSH) and some characteristics of the ternary complexes (εmax and ΔpH50).

Liquid-Liquid Extraction, Niobium, Tantalum, Complex Formation, Ion-Associate, Constants of Dissociation, Relationship, Spectrophotometric Investigation

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