Complexes of metallochromic substances. II

Summary The optimum conditions for complex formation between La³⁺, arsenazo I, and monoarsenazo III were found. The composition, the formation and stability constants of the complexes formed were ascertained. Comparison of the complexing properties of monoarsenazo III and arsenazo III showed the high importance of every arseno-group in the molecule of the reagent.

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Zusammenfassung Die optimalen Bedingungen für die Komplexbildung zwischen La³⁺, Arsenazo I und Monoarsenazo III wurden ausgearbeitet. Es wurden die Zusammensetzung sowie die Bildungs- und Stabilitätskonstanten der gebildeten Komplexe bestimmt. Ein Vergleich der komplexbildenden Eigenschaften des Monoarsenazo III und Arsenazo III zeigte die große Bedeutung jeder Arsonogruppe im Molekül des Reagens.

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See alsoBudínský, B.: Z. analyt. Chem.206, 262 (1964).

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The author wishes to thank Miss L.Krumlová for technical assistance at this work.     

A systematicstudy of insoluble substances. II

The antimonates of Be, Mg, Zn, Cd. Cr, Mn, Co, Ni, Cu, Ca, Sr, Ba, Al. 'I'h. Zr and U when heated to 900° were found to become sufficiently resistant to the standard acid treatment to be considered insoluble. The corresponding stannates do not become insoluble on being subjected to this treatment. The corresponding arsenates with the exception of those of Zi, Ti, Cr and Sn also do not become insoluble on being heated.     

The electrochemistry of proteins and related substances: Part II. Insulin

The electroreduction of insulin in pH 7.4 solution was studied at the hanging mercury drop electrode by cyclic voltammetry and at a mercury pool electrode by controlled potential coulometry. The proposed mechanism involves reduction of an adsorbed monolayer of insulin (maximum coverage of 10 μC cm^?2) in a four-electron reaction at about ?0.6 V vs. SCE resulting in breakage of two of the three disulfide bonds in the molecule. Fast reoxidation leads to recovery of much of the reduced species. At longer time (ca. 100 s) a steady state is reached where the reductions and reoxidation involve reversible two-electron reactions.     

Toxicological evaluation of harmful substances by in situ enzymatic and biological detection in high-performance thin-layer chromatography

The efficiency of a chromatographic analysis method is determined by the selectivity of the chromatographic separation and the specificity of the detection method. In the case of high-performance thin-layer chromatography (HPTLC) the separated components can be detected and quantified directly on the chromatogram by physical and chemical methods. By coupling high-performance thin-layer chromatography with biological or biochemical inhibition tests it was possible to detect toxicologically active substances in situ. A linear relationship was shown between the signal of the inhibition of cholinesterase and the concentration of the inhibitor using a constant enzyme concentration and a constant incubation time. The graph of the inhibition of the luminescence of Photobacterium vibrio fisheri in relation to the concentration of pentachlorophenol (range 20–80 ng) is nearly linear. Measurements were done by using a densitometer or a videodensitometric scanner.     

Reactivity and gelation. II. Substitution effect

The development in Paper I is extended to multifunctional condensations where the functional groups exhibit unequal reactivities induced by substitution effects in the course of the polymerization. A system R(A)₂/R′(B)₃ is examined to determine how the gel point varies with the strength and positive or negative sense of the substitution effect. As in Paper I, intramolecular interactions are not considered.     

Isoparametric kinetic relations for chemical transformations in condensed substances (Analytical survey). II. Reactions involving the participation of solid substances

Various manifestations of the kinetic compensation effect are considered in reactions involving the participation of solid substances under isothermal and nonisothermal conditions, as well as manifestations of other isoparametric correlations. It is shown that isoparametric correlations can be used for the analysis of solid-phase reactions and the exclusion of artefacts in nonisothermal kinetics.

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Zusammenfassung Verschiedene Erscheinungen des kinetischen Kompensationseffektes bei unter Beteiligung von festen Substanzen unter isothermen und nichtisothermen Bedingungen verlaufenden Reaktionen werden erörtert, ebenso Erscheinungen anderer isoparametrischer Korrelationen. Es wird gezeigt, daß isoparametrische Korrelationen zur Analyse von Festphasenreaktionen und zum Ausschluß von Artifakten in der nicht-isothermen Kinetik herangezogen werden können.

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Study on radiation-induced polymerization of vinyl monomers adsorbed on inorganic substances. II. Radiation-induced polymerization of methyl methacrylate adsorbed on several inorganic substances

The radiation-induced polymerization of methyl methacrylate (MMA) absorbed on such inorganic substances as silica gel, white carbon, silicic acid anhydride, zeolite, and activated alumina was carried out to compare with the case of styrene. The rate of radiation-induced polymerization adsorbed on inorganic substances was high compared with that of radiation-induced bulk state polymerization, as was the case with styrene. Inorganic substrates which contain aluminum as a component element are more likely to be grafted than those which consist of SiO₂ alone, as with styrene. The molecular weight distribution of unextractable polymer and extractable polymer differs, depending on the type of inorganic substance. Experiments by a preirradiation method were carried out in case of silica gel, white carbon, and silicic acid anhydride. GPC spectra of the polymer obtained were different from those of polymer formed by the simultaneous irradiation method. It appears that all the unextractable polymer is grafted to the inorganic surface with chemical bond.     

The study of complex mixtures of natural substances by the defocusing and DADI methods. II. Phytosterols accompanying β-sitosterol

Low- and high-resolution mass spectra and defocusing and DADI spectra of samples of -sitosterol isolated from various plant material have been studied. The spectral information obtained has shown the presence in samples of -sitosterol studied of minor accompanying components which have been identified as stigmasterol, campesterol, and cholesterol.Institute of Bioorganic Chemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 81–85, January–Feburary, 1981.