[en] A highly sensitive rapid method for determination of rhenium in sulfuric acid solution containing Re(7) is proposed. The method includes hydrocloric acid introduction into initial solution (2-10 vol. %), Re(7) reduction to Re(6) by ultraviolet irradiation (230-300 nm) and subsequent Re(6) detection by spectrophotometric or electron paramagnetic resonance method. The rhenium detection limit is 1 μg/ml, error of determination is ±2%

[en] Using the method of pulsed photolysis Re(7) photoreduction in the presence of electron donors-diphenylamine (DPA) and hydroquinone (HQ) in concentrated HCl solutions is studied. A short-lived rhenium (6) complex ReOCl₅^- appeared in photolysis eneters in reaction of single-electron oxidation of both DPA with DPA⁺ radical-cation formation and HQ with semiquinone radical formation. DPA⁺ radical-cations disappear in in the second-order reaction with stable product formation (λ_max=590 nm)

[en] To simplify the technique and to expand the number of methods for determining rhenium in process sulfuric acid solutions, the possibility is studied of creating a method based on photochemical preparing of Re(6) oxo-chloride complex. 18M H₂SO₄, 11.3M HCl solutions and aqueous 1x10^-2 M HReO₄ solution were used. The absorption spectra of rhenium solutions before and after irradiation by light with ν=39400 cm^-1 are presented. Optimum conditions for the photochemical reaction are found: solutions of concentrated H₂SO₄, containing 2 vol.% of concentrated HCl and less than 25 vol.%H₂O. The possibility is shown of applying the photochemical reduction of Re(7) to Re(6) in solutions of concentrated H₂SO₄ in the presence of HCl for rhenium quantitative determination. The linear dependence between the optical density of the solution after irradiation and Re content in the solution is observed in the range of Re concentration from 1 to 37 μg/ml. The detection limit is 1 μg/ml. A photochemical technique for rhenium determination in a sample of process sulfuric acid is devised

[en] A nitrate-induced oxidation of diphenylamine by hydroxylamine catalyzed by oxochloride complex of rhenium (6) was found. An optimal ratio of concentrated. H₂SO₄ and HCl (3:1) was established which provided equilibrium existence of oxochloride complexes of Re(7), Re(6) and Re(5). A kinetic method was developed of determining rhenium in sulfuric acid solutions by using a rhenium-catalyzed HNO₃-induced oxidation of diphenylamine with hydroxylamine. The limit of Re detection is 3.10^-9 mole/l

[en] Using the temperature growth method, equilibria in the system Re⁵-HCl-H₂O have been studied. In solutions of 4-8 N HCl rapid (tau₁<10 μs) and slow (tau₂=2-20 ms) relaxation processes are detected, Where in concentrated HCl (11.3 N) - only the rapid one. Analysis of relaxation amplitude spectra permitted to establish the existence of four Re⁵ forms in hydrochloric acid solutions

[en] A possibility of photochemical reduction of Re(VII) to Re(VI) in mixture of concentrated sulfuric and hydrochloric acids has been demonstrated. The reaction mechanisms of Re(VII) photoreduction and Re^VIOCl_s^- complex decay have been considered from view point of acids and water content. The optimal conditions of Re^VIOCl₅^- stability have been found. Spectrophotometric and ESR methods of rhenium determination based on photochemical production of Re^VIOCl₅^- complex with the detection of 1μg/ml have been proposed. Rhenium concentration in industrial sulfuric acid has been determined. (Author)

[en] Stereometry of electron transfer elementary act in the reaction of molybdenum (6) complex photoreduction in hydrochloric acid at 77 K is studied. Anisotropy of electron transfer as well as formation of partially-orientated ion-radicals Cl₂^- under irradiation of vetrified solutions with polarized light is detected. Estimation of the distance between molybdenum (5) complexes, forming during photolysis, and ion-radicals Cl₂^-, which value turns out to be equal to 12 A, is carried out