A simple and sensitive analytical method for the determination of antimony in environmental and biological samples.

The results of a study and application of leucocrystal violet for the determination of antimony in parts per million levels is described here. The proposed method is based on the reaction of antimony(III) with acidified potassium iodate to liberate iodine. The liberated iodine selectively oxidizes leucocrystal violet to crystal violet dye. The formed dye shows maximum absorbance at 590 nm. The color system obeys Beer's law in the concentration range from 0.4 - 3.6 microg antimony per 25 ml of final solution. The molar absorptivity and Sandell's sensitivity were found to be 7.32 x 10(5) l mol(-1) cm(-1) and 0.0016 microg cm(-2), respectively. All variables were studied in order to optimize the reaction. The proposed method is satisfactorily applicable for the analysis of antimony in various environmental and biological samples. The method is simple, highly sensitive, accurate and reliable.     

Bounds on the inverses of nonnegative triangular matrices with monotonicity properties

Some bounds on the entries and on the norm of the inverse of triangular matrices with nonnegative and monotone entries are found. All the results are obtained by exploiting the properties of the fundamental matrix of the recurrence relation which generates the sequence of the entries of the inverse matrix. One of the results generalizes a theorem contained in a recent article of one of the authors about Toeplitz matrices.     

Influence of cobalt(III) dimethyldithiocarbamate complexes on styrene polymerization initiated by tert-butyl perbenzoate

Kinetic features of radical polymerization of styrene initiated by tert-butyl perbenzoate in the presence of tris(N,N-dimethyldithiocarbamato)cobalt(III) (CoL₃) and its adduct with iodine (CoL₃ · 2I₂) were studied. The optimal concentration ratios of the activators and tert-butyl perbenzoate, providing fast styrene polymerization at 338–368 K, were determined.     

Self-inhibition or the lack of it in the pyrolyses of neopentane and n-hexane

Published data show that in its early stages (up to 3% decomposition), the pyrolysis of n-hexane in the ranges 723–823 K and 10–100 Torr is not inhibited by the olefin products, in contrast with neopentane pyrolysis which is very strongly inhibited in similar conditions. Detailed consideration of the chain mechanisms for the two pyrolyses shows that the reactivity of the chain terminating radical towards hydrogen abstraction from an allylic C? H bond in product olefin is the factor which determines whether or not observable self-inhibition occurs. Thus, n-hexane pyrolysis, whose chain decomposition is terminated by recombination and disproportionation of ethyl, is not significantly self-inhibited, whereas that of neopentane which is terminated by recombination of methyl is very strongly inhibited because methyl is 14× more reactive than ethyl. The implications for other alkanes are briefly discussed.     

HPLC studies of isomeric chromium-N-benzoylphenylhydroxylaminates

Summary N-Benzoylphenylhydroxylarnine complexes of some metals have been investigated by HPLC. The green chromium complex formed by this reagent shows conclusive evidence of the presence of geometrical isomers. It is photosensitive and changes to a brown modification when irradiated with ultra violet or visible light. Elution behaviour of the complexes has been studied with different solvent mixtures. Attempts have been made to characterize the complexes from different measurements.

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Untersuchung von isomeren Chrom-N-benzoylphenylhydroxylaminaten durch HPLC

     

An unusual transformation of perfluorinated 1- and 3-phenylpropenes to polyfluorochloroindanes by the action of AlCl3

The reaction of perfluorinated 1- and 3-phenylpropenes with AlCl₃ gives polyfluorochloroindanes as the result of an intramolecular cyclization, apparently, by an electrophilic pathway.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2854–2857, December, 1989.     

Orthogonal decompositions of a space of symmetric tensors on an almost-Kählerian manifold

Kemerovo. Translated from Sibirskii Matematicheskii Zhurnal, Vol. 30, No. 3, pp. 131–139, May–June, 1989.     

Structure and molecular motion of poly(ethylene oxide) chains adsorbed on a silica-tethered poly(methyl methacrylate) by the spin label method

The spin-label method was used to study the structure and molecular motion of poly(ethylene oxide) (PEO) chains adsorbed on a silica-tethered poly(methyl methacrylate) (PMMA). Spin-labelled PEO with a narrow molecular weight distribution, having number averaged molecular weight (M _N)=6.0×10³, was adsorbed on the surface of the silica-tethered PMMA with various grafting ratios in carbon tetrachloride solution at 35?°C. ESR spectra were measured at various temperatures after the samples were completely dried. The ESR spectra are composed of two spectra arising from spin-labels attached to “train” and “tail” segments, which are strongly and weakly interacted with the silica surface, respectively. The fractional amount of the “tail” segments increases extremely with the grafting ratio of PMMA. Molecular mobility of the PEO chains estimated from the temperature dependence of the ESR spectra also decreases significantly with the grafting ratio of PMMA. Structure and molecular motion of the PMMA chains tethered on the silica were also studied using the spin-labelled PMMA. Consequently, parts of the PEO segments penetrate into the PMMA chains and is adsorbed on the silica surface (“train” segments), whereas parts of the PMMA segments protrude from the surface. The other PEO segments are entangled with the tethered PMMA chains (“tail” segments).