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[en] The kinetic and mechanistic aspects of cerium(III)- catalysed oxidation of 4-oxo acids by bromate (uncontaminated with bromine) in an acid medium have been studied. The reaction exhibited first-order each in [bromate] and [acid], fractional order each in [oxo acid] and [cerium(III)], and also showed solvent isotope effect of 0.55 (k(H₂O)/k (D₂O)). The reaction did not induce polymerization and the induction period was not observed. The influence of ionic strength on the rate was negligible, while increase in reaction rate was found by lowering the dielectric constant of the me- dium. The reaction rate was affected by the presence of substituents in the reaction centre. Increase in the reaction rate by electron releasing substituents and decrease in the rate by the presence of electron-with- drawing substituents were observed. The Hammett plots were characterized by smooth curvature; how- ever, linearity was observed using exalted σ values. A negative value for the reaction constant was observed. The isokinetic relationship was evaluated from the Arrhenius and Hammett plots. The formation of a ternary complex between oxidant, substrate and catalyst has been proposed in the mechanism. Based on the proposed mechanism, the rate law has been derived. The formation of a π-complex between Ce(III) and -ene of the enol form of oxo acid has been proposed. This reaction finds application in the synthesis of substituted benzoic acids and involves the phenomena of intramolecular catalysis and neighbouring group participation. (author)

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[en] A measurement method for simultaneous determination of impurities (Cu, As, Se, Ag, Cd, Sn, Te, Pb, Bi) in high purity antimony by using inductively coupled plasma mass spectrometry (ICP-MS) was studied. The samples were dissolved by nitric acid, aqua regia solution, nitric acid and hidrochloric acid mixed bromic acid then were measured directly on ICP-MS.The effect of matrix element antiony was evaluated. The recoveries were 90%-98% when samples were treated by aqua regia solution and HNO₃+HCl+HBr. The relative standard deviations were smaller than 10%. The procedure was applied to determination of impurities in high purity antimony higher than 99%, meets the requirements of some domestic antimony export enterprises. (author)

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[en] The nonlocal resonance model developed earlier for the description of low-energy inelastic and reactive electron-HCl collisions has been adapted to the electron-HBr collision system. The parameters of the model have been determined by fitting the eigenphase sum in the fixed-nuclei approximation to the data of an ab initio R-matrix calculation of Morgan, Burke, and collaborators. The Schwinger-Lanczos method has been employed to solve the nuclear scattering problem with a nonlocal, complex, and energy-dependent effective potential. Fully converged cross sections have been obtained on a dense grid of energies for many vibrational excitation, deexcitation, and dissociative channels in both HBr and DBr. The computed cross sections are generally in good agreement with experiment as far as data are available. copyright 1996 The American Physical Society

[en] A method, based on anion exchange chromatography, is presented for the isolation of ¹³⁹Ce after production by a proton-induced nuclear reaction on a thick praseodymium target. After bombardment the target is dissolved in nitric acid and ¹³⁹Ce oxidised to the Ce(IV) oxidation state with bromic acid. ¹³⁹Ce is then separated form the praseodymium by anion exchange chromatography on a Ag MP-1 resin column in a nitric acid - bromic acid mixture. ¹³⁹Ce is sorbed onto the resin column and praseodymium eluted with the acid mixture. The bromic acid is washed out of the column with nitric acid and ¹³⁹Ce finally eluted with dilute nitric acid containing sulphur dioxide

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[en] Short communication. 2 refs