Vaporization thermodynamic studies by high-temperature mass spectrometry on some three-phase regions over the MnO-TeO2 binary line in the Mn-Te-O ternary system

Knudsen effusion mass spectrometric measurements have been performed in the temperature range of 850-950 K over four three-phase mixtures, each phase mixture having at least one phase lying on the MnO-TeO2 binary line of the Mn-Te-O phase diagram, and the rest of the phases lying above this binary line. The three-phase mixtures investigated are Mn3O4 + MnO + Mn6Te5O16; Mn3O4 + Mn6Te5O16 + MnTeO3; Mn3O4 + Mn3TeO6 + MnTeO3; and Mn3TeO6 + MnTeO3 + Mn2Te3O8. The vapor pressures of the gaseous species TeO2, TeO, and Te2 over these three-phase mixtures were measured, and various heterogeneous solid-gas reactions were evaluated along with the homogeneous gas-phase reaction TeO2(g) + 0.5Te2(g) = 2 TeO(g). The enthalpy and Gibbs free energy of formation of the four ternary Mn-Te-O phases were deduced at T = 900 K. These values (in kJ.mol-1), along with the estimated uncertainties in them are Delta(f)H(o)m = 4150 +/- 19, 752 +/- 11, 1710 +/- 11, 1924 +/- 40, and Delta(f)G(o)m= 2835 +/- 28, 511 +/- 11, 1254 +/- 19, 1238 +/- 38, for Mn6Te5O16, MnTeO3, Mn3TeO6, and Mn2Te3O8, respectively. A thermochemical assessment was made to examine the conditions under which the ternary Mn-Te-O phases could be formed on a stainless steel clad of mixed-oxide-fueled (MO2; M = U + Pu) fast breeder nuclear reactors. The phase Mn3TeO6 could be formed when the fuel is even slightly hyperstoichiometric (O/M = 2.0002) and the phase Mn6Te5O16 could also be formed when O/M = 2.0004. The threshold tellurium potential for the formation of Mn3TeO6 is higher than that for MnTe0.80 and CrTe1.10, but is comparable to that for MoTe1.10, and even lower than that for FeTe0.81 or NiTe0.63.     

Degradation studies of14C labelled p-fluorophenylacetic acid prepared by exchange reaction

Carbon-14 labelled p-fluorophenylacetic acid was prepared by heating its sodium salt with¹⁴CO₂ at 325 °C. The labelled acid after isolation from the reaction mixture was degraded by reaction with sodium azide. From the radioactivity measurements it was observed that no scrambling of¹⁴C had taken place and the acid could be designated as carboxyl-¹⁴C.Paper presented at the DAE Symposium on Nuclear Chemistry and Radiation Chemistry in February 1988 at Bombay, India.     

Benzyl chloride transformation as a probe for electron transfer on Rh/TiO2 under SMSI state

Benzyl chloride transformation has been studied over Rh/TiO₂ under SMSI state to give evidence for the transfer of electrons from support to metal.

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Rh/TiO₂, . .

     

Lithium-substituted cobalt oxide spinels LixM1−xCo2O4 (M = Co2+, Zn2+; 0 ≤ x ≤ 0.4)

Substitution of Li⁺ into Co₃O₄ and ZnCo₂O₄ gives rise to the solid solution series Li_xM_1?xCo₂O₄ (M = Co²⁺ or Zn²⁺) having the spinel structure upto x = 0.4. X-Ray diffraction intensities show that the spinel solid solutions are likely to have the following cation distributions: (Co²⁺)_t[Li⁺_xCo³⁺_2?3xCo⁴⁺_2x]₀O₄ and (Zn²⁺_1?xCo²⁺_x)_t[Li⁺_xCo³⁺_2?3xCo⁴⁺_2x]₀O₄. Electrical resistivity and Seebeck coefficient data indicate that the electron transport in these systems occurs by a small-polaron hopping mechanism.     

Molecular structure of N,N-bis(benzimidazol-2-ylethyl)sulfide dihydrochloride dihydrate,a heavy metal chelating ligand

The title compound contains two benzimidazole nitrogens and one thioether sulfur atom, which are potential sites for metal ion binding. Both the benzimidazole nitrogens of the molecule are protonated. The benzimidazole rings are almost parallel to each other, the dihedral angle being 6.9(1)°. The C–S–C bond angle is 100.6(2)° and the C–S–C–C torsion angles are –75.9(3)° and –80.6(3)°, leading to gauche conformation which is one of the favored conformations in the crystalline state of simple monothioethers.     

Figure-eight aromatic core-modified octaphyrins with six meso links: syntheses and structural characterization

The synthesis and structural characterization of the first examples of aromatic core-modified figure-eight octaphyrins with six meso links and their formation with and without acid catalysts are highlighted.     

Effect of gamma-irradiation on the catalyzed bromate oscillator

The oscillatory characteristics of a catalyzed bromate system is altered by gammairradiation. The alterations observed are probably due to the activation of the reduced form of the metal ion catalyst under gamma-irradiation. However, these alterations could not be accounted for in terms of an effective concentration of bromate acting as a quenching agent under gamma-irradiation conditions as reported in the literature.     

Gamma radiation-induced bulk polymerization of some methyl aryloxymethacrylates

The kinetics of γ-radiation-induced bulk polymerization of methyl phenoxymethacrylate and methyl paracresoxymethacrylate was studied at dose rates of 0.3 and 0.075 Mrad/h and at temperatures of 0 and 30°C. The polymerization was first order with respect to the monomers and the rate of polymerization had a direct dependence on dose rate. The activation energy value for the polymerization of methyl phenoxymethacrylate was 1.2 and 0.7 kcal/mol for methyl paracresoxymethacrylate. The polymerization proceeded predominantly by an ionic mechanism.