On the reactions 2 C + O2 and C + CO2 at very low pressure

In an ultra high vacuum heterogeneous gas reactions such as 2 C + O₂^G → 2 CO^G and C + CO₂^G → 2 CO^G often show a less complicated reaction path than under normal pressure. In the present study the graphite sample is a commercial light‐bulb filament, which is extremely resistant against oxidation. Under low pressure the combustion reaction is of first order with a continuous transition to zero order at temperatures between 900 and 1300 K depending on the oxygen pressure. The Boudouard reaction behaves similarly but obeys zero order only around 2000 K and for CO₂ pressures around 1 bar. The measured and the statistically calculated reaction rates agree well. An insight of the details of the reaction and chemisorption is determined by the evaluation of experiments carried out in an ultra high vacuum using isotopes such as ¹³CO₂^G. The Boudouard equilibrium for graphite can be reached only catalytically, e.g., with sponge iron in statu nascendi.     

Reaction between CaO‐SiO2‐Al2O3 Slags and H2 + HCl + H2O Gas Mixtures

To better understand the thermodynamic behaviour of chlorine in blast furnaces, CaO‐SiO₂‐Al₂O₃ slags were brought into equilibrium with Ar + H₂ + HCl + H₂O gas mixtures at temperatures between 1673 K and 1798 K. The dissolution of chlorine into molten slags could be well interpreted through a reaction: (1/2) {CaO}_slag + (HCl) = {Ca_1/2Cl}_slag + (1/2) (H₂O). Conforming to this formula, a linear relation was observed between log (%CI) and log with an anticipated slope of 1/2.     

Phase Equilibrium of Ternary Systems LaX 3 C 18 H 16 N 3O 2Cl H 2O

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NaGa(C7H3NO4)2·2H2O光催化剂的制备与性能

2,6-吡啶二甲酸钠与三氯化镓在pH≈3的条件下直接反应,合成了NaGa(C7H3NO4)2·2H2O配合物单晶.通过元素分析、红外及X射线衍射分析确定了配合物的结构.以该配合物作为催化剂,用罗丹明B模拟染料废水进行了光催化降解脱色试验,对影响反应的各种条件(如催化剂的投加量,染料的初始浓度,通氧速率及光源)进行了考察.结果表明,在催化剂为20mg,染料初始浓度为2.0×10-4mol·L-1,通氧速率为200ml·min-1,光源为500W汞灯时,配合物NaGa(C7H3NO4)2·2H2O具有优良的催化活性,1h内对罗丹明B的降解率可达98.9%.     

The crystal and molecular structure of a valinomycin analogue cyclo[(D-Val-L-Lac-L-Ala-D-Hyi)2(D-Val-L-Lac-L-Val-D-Hyi)]. H2O(C50H82N6 O18.H2O)

The crystal and molecular structure of the valinomycin analogue, cyclo[(D-Val-L-Lac-L-Ala-D-Hyi)2(D-Val-L-Lac-L-Val-D-Hyi)] has been solved by x-ray direct methods using the "Shake and Bake" procedure. The crystals, grown from a mixture of octane/CH2Cl2, belong to space group P2(1) (Z = 4) with cell parameters a = 10.29, b = 32.08, c = 18.73 A, beta = 97.05 degrees, and contain two molecules per asymmetric unit. After anisotropic refinement the standard reliability factor was Rl = 0.058. The conformations of both independent molecules is similar to that observed for isoleucinomycin, cyclo[-(D-Ile-L-Lac-L-Ile-D-Hyi)3] [V. Z. Pletnev et al. (1980) Biopolymers, Vol. 19, pp. 1517-1534]. The structure has an asymmetric conformation stabilized by six intramolecular H bonds, five bonds being of the 4-->1 type and one bond being of the 5-->1 type. One water molecule is caged in the internal cavity of each cyclodepsipeptide. This conformation could represent an intermediate state between free and complexed forms of valinomycin.     

Glutathione is a cofactor for H2O2-mediated stimulation of Ca2+-induced Ca2+ release in cardiac myocytes

Reactive oxygen species are known to cause attenuation of cardiac muscle contraction. This attenuation is usually preceded by transient augmentation of twitch amplitude as well as cytosolic Ca2+. The present study examines the role of an endogenous antioxidant, glutathione in the mechanism of H2O2-mediated augmentation of Ca2+ release from the sarcoplasmic reticulum. Whole-cell patch-clamped single rat ventricular myocytes were dialyzed with the Cs+-rich internal solution containing 200 microM fura-2 and 2 mM glutathione (reduced form). After equilibration of the myocyte with intracellular dialyzing solution, Ca2+ current-induced Ca2+ release from the sarcoplasmic reticulum was monitored. Rapid perfusion with H2O2 (100 microM or 1 mM) for 20 s inhibited Ca2+ current, but enhanced the intracellular Ca2+ transients for 3-4 min. Thus, the efficacy of Ca2+-induced Ca2+ release mechanism was augmented in 71% of myocytes (n = 7). This enhancement ranged between 1.5- to threefold as the concentrations of H2O2 were raised from 100 microM to 1 mM. If glutathione were excluded from the patch pipette or replaced with glutathione disulfide, the enhancement of Ca2+-induced Ca2+ release was seen in only a minority (20%) of the myocytes. H2O2 exposure did not increase the basal intracellular Ca2+ levels, suggesting that the mechanism of H2O2 action was not mediated by inhibition of the sarcoplasmic reticulum Ca2+ uptake or activation of passive Ca2+ leak pathway. H2O2-mediated stimulation of Ca2+-induced Ca2+ release was also observed in myocytes dialyzed with dithiothreitol (0.5 mM). Therefore, reduced thiols support the action of H2O2 to enhance the efficacy of Ca2+-induced Ca2+ release, suggesting that redox reactions might regulate Ca2+ channel-gated Ca2+ release by the ryanodine receptor.     

Pressure Leaching Kinetics of Multimetallic Sulphide Concentrates in H2SO4 + O2 Solution

Abstract

A multimetallic sulphide concentrate containing sphalerite, galena, chalcopyrite and silver in the matrix of pyrite was decomposed at elevated temperature and oxygen pressures in dilute sulphuric acid solutions for sufficient residence time to yield 95% of the zinc in the pregnant solution while most of the lead and silver remained in the residue together with most of the pyrite. The selective leaching process appeared to follow the diffusion controlled mechanism. The effects of concentration of the leachant, temperature and time of leaching, particle size, oxygen pressure and agitation on the leaching process were investigated. Results indicate the prospect of extracting not only all the metals but also appreciable amounts of elemental sulphur under optimized experimental conditions.     

Corrosion of Fe-Ni-Cr,Fe-Cr-AI,and Fe-Ni-Cr-AI Alloys in H2/H2O/H2S Mixtures at 1200 °C

A series of Fe-Ni-Cr, Fe-Cr-AI, and Fe-Ni-Cr-Al alloys has been exposed at 1200 °C in atmospheres of controlled oxygen and sulfur potentials, after preoxidation in air or in impure argon. The corrosion behavior has been interpreted on the basis of phase-stability diagrams. The presence of iron and nickel-rich spinel particles in the outer layers of the initial oxide scales plays an essential role in the resistance to sulfur attack. When the oxygen potential is sufficiently low, these spinels are reduced to a mixture of chromium oxide and an Fe-Ni alloy. The latter can then form sulfides which are liquid at high temperatures and which accelerate the penetration of sulfur into the underlying metal. C. ROQUES-CARMES, formerly at the Laboratoire de Métallurgie Physique, Orsay.     

H2C2O4表面处理镁钙砂及其浇注料性能研究

采用H2C2O4溶液表面浸渍MgO-CaO砂并制成浇注料,研究了表面处理后MgO—CaO砂及其浇注料的物理性能。结果表明,膜由细小颗粒组成,均匀、密集,膜与镁钙砂颗粒表面之间无间隙,结合良好,膜的厚度约为5～10μm,其水化粉化指数低于日本H2PO4浸渍处理的同类材料的粉化指数,水化增重率也达到日本同类材料的水平;采用这种镁钙熟料制成的镁钙浇注料具有良好的抗水化性能,常规物理性能优于未经任何处理的镁钙浇注料和镁质浇注料,抗渣渗透性也比镁质浇注料更强。     

Oxygen potentials in Ni + NiO and Ni + Cr2O3 + NiCr2O4 systems

The chemical potential of O for the coexistence of Ni + NiO and Ni + Cr₂O₃ + NiCr₂O₄ equilibria has been measured employing solid-state galvanic cells, (+) Pt, Cu + Cu₂O // (Y₂O₃)ZrO₂ // Ni + NiO, Pt (-) and (+) Pt, Ni + NiO // (Y₂O₃)ZrO₂ // Ni + Cr₂O₃ + NiCr₂O₄, Pt (-) in the temperature range of 800 to 1300 K and 1100 to 1460 K, respectively. The electromotive force (emf) of both the cells was reversible, reproducible on thermal cycling, and varied linearly with temperature. For the coexistence of the two-phase mixture of Ni + NiO, δΜ_{O 2}(Ni + NiO) = −470,768 + 171.77T (±20) J mol⁻¹ (800 ≤T ≤ 1300 K) and for the coexistence of Ni + Cr₂O₃ + NiCr₂O₄, δΜ_{O 2}(Ni + Cr₂O₃ + NiCr₂O₄) = −523,190 + 191.07T (±100) J mol⁻¹ (1100≤ T≤ 1460 K) The “third-law” analysis of the present results for Ni + NiO gives the value of ‡H ₂₉₈ ^o = -239.8 (±0.05) kJ mol⁻¹, which is independent of temperature, for the formation of one mole of NiO from its elements. This is in excellent agreement with the calorimetric enthalpy of formation of NiO reported in the literature.