A volumetric determination of arsenic and antimony in mixed manganese arsenide,antimonide and phosphide compounds

A procedure is described for the titrimetric determination, of arsenic and antimony without separation. Total combined arsenic and antimony were determined by reduction with tin(II) chloride and titration with permanganate; antimony is found by selective reduction with mercury(I) chloride and titration with permanganate. A precision of 0.1–0.2% was obtained for total combined arsenic and antimony, and approximately 1% for antimony alone (small amounts in the presence of large amounts of arsenic). The procedure was developed for and applied to the analysis of synthesized compounds of the type MnAs_1-xP_x and MnAs_1-ySb_y.     

Thermogravimetric analysis of polycarbonates and polythiocarbonates from diphenols with methyl groups

The thermal behaviour of polycarbonates and polythiocarbonates derived from biphenols with methyl groups in the aromatic rings was studied by dynamic thermogravimetry. The thermal degradation temperatures (TDT) were determined, showing that polythiocarbonates are more stable than the corresponding polycarbonates. The kinetic parameters of the thermal decomposition were determined by using the Arrhenius relationship, and showed two steps for the degradation of the polycarbonates, the first being a zero-order process and the second having first-order kinetics; the steps were associated with two different reaction mechanisms. Polythiocarbonates degraded according to first-order kinetics.     

Calorimetric and diffractometric study of the lowest room-temperature transition of polytetrafluoroethylene

Through differential scanning calorimetry and wide angle x-ray scattering, the room-temperature transitions of native (never melted) polytetrafluoroethylene have been investigated. The independence of the transitions, and in particular of the lowest one, on the heating kinetics, seems to suggest that also this transition is a true crystal-crystal transition.     

Uptake of thorium ions from aqueous solutions by a molecular sieve (13X type) powder

The adsorption of thorium(IV) ions on molecular sieve (13X type) powder from aqueous solutions has been studied as a function of shaking time pH, thorium ion concentration and temperature. The conditions of maximum adsorption of thorium ions obeys Langmuir and D-R isotherms over the entire concentration range studied. Thermodynamic quantities such as H, G and S have been calculated fromK _D values determined at various temperatures. The results show endothermic heat of adsorption, but negative free energy value indicates that the process of thorium adsorption on molecular sieve powder is favored at high temperature. The influence of various cations and anions on thorium(IV) ion adsorption was examined. A wavelength dispersive X-ray fluorescence spectrometer was used for measuring the thorium ion concentration in solutions.     

Alkaloids ofThalictrum isopyroides

Summary 6,7-Dimethoxy-2-methyl-1,2-dihydroisoquinolin-1-one and the new aporphine base 9-hydroxy-1,2,3,10-tetramethoxyaporphine, which has been called thalisopynine, have been isolated fromThalictrum for the first time.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnyk Soedinenii, No. 4, pp. 472–474, July–August, 1978.     

Absorption and fluorescence spectroscopy of rhodamine 6G in titanium dioxide nanocomposites

A comparison has been made between the spectroscopic properties of the laser dye rhodamine 6G (R6G) in mesostructured titanium dioxide (TiO(2)) and in ethanol. Steady-state excitation and emission techniques have been used to probe the dye-matrix interactions. We show that the TiO(2)-nanocomposite studied is a good host for R6G, as it allows high dye concentrations, while keeping dye molecules isolated, and preventing aggregation. Our findings have important implications in the context of solid state dye-lasers and microphotonic device applications.     

Neutron activation cross-section of zirconium-94

The thermal neutron activation cross-section of⁹⁴Zr was found to be 49.3±0.6 millibarns. It is shown that neutron activation analysis of Zr in silicate samples with a Zr/U ratio<10 has considerable uncertainty due to fission contribution. A correction factor for the fission contribution has been determined experimentally.     

The esterase and peptidase activities of an elastolytic enzyme of Actinomyces rimosus

Summary 1. It has been shown that the values of K_m for the esterase activity of elastase ofActinomyces rimosus and for pancreatic elastase are of the same order of magnitude.2. The elastase ofActinomyces rimosus, unlike the pancreatic enzyme, is capable of hydrolyzing only the methyl ester of N-acetyltrialanine, and not the mono and di derivatives.3. It has been found that in the initial stage of the hydrolysis reaction it is mainly the ester bonds that are cleaved.Institute of Molecular Biology, Academy of Sciences of the USSR, Moscow. N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 693–695, September–October, 1977.     

The influence of seasonal changes in the concentration of trace elements in liver tissue of various wild animals determined by instrumental neutron activation analysis

Levels of some of the most essential minerals in liver tissue of wild animals living in game reserves in South Africa were studied by instrumental thermal neutron activation analysis and a Ge(Li) detector. In addition, some of the most important trace elements were determined by atomic absorption spectrometry. The distribution of the content of the various elements was followed for about two years and attempts have been made to explain the influence of seasonal fluctuations of the micronutrients determined.     

Synthesis of racemic and optically active Δ1- and Δ6-3,4-cis-tetrahydrocannabinols1

Three syntheses of the hitherto unknown (±)-Δ⁶-3,4-cis-THC 4a and the first total synthesis of optically active Δ¹- and Δ⁶-cis-THC's are described. These syntheses utilize a stereospecific intramolecular epoxide opening by phenolate anion; an acid catalyzed equilibration of Δ¹- and Δ⁶-cis-THC acetates; and a kinetically controlled dehydration. The use of HPLC, GLC and NMR for the separation and identification of closely related THC's is discussed.