氧化酸性铬蓝K褪色光度法测定钒

在１８０～２５０ｍｏｌ／ＬＨ２ＳＯ４介质中,Ｖ（Ⅴ）对酸性铬蓝Ｋ有褪色作用。褪色程度与Ｖ（Ⅴ）量相关,借此建立了吸光光度测定Ｖ的方法。实验表明,褪色反应随温度升高而加快,在沸水浴中１０ｍｉｎΔＡ可达最大值,流水冷却后吸光度保持２４ｈ不变,有色溶液的最大吸收波长为５２０ｎｍ,ε＝１０×１０４Ｌ·ｍｏｌ－１·ｃｍ－１,Ｖ（Ⅴ）量在０～３２ｍｇ／Ｌ内与有色溶液吸光度的减少值呈线性关系。所拟方法用于测定铁矿石中微量Ｖ时,结果与苯甲酰基苯胲比色法一致。     

熔体─上地幔岩石的相互作用及稀土元素模拟计算──以法国中央高原堡雷(Bore)幔源包体为例

产于法国中央高原堡雷（Boree）的具镶嵌结构方辉橄榄岩包体被认为是大陆活动区碱性玄武岩捕获的、来源最深的尖晶石相上地幔样品。已有的岩浆堆积说和等物理化学环境中重结晶模式难于解释其矿物学、微量元素和Sr－Nd同位素地球化学特征,为此我们提出了热柱来源熔体渗滤岩石圈底部的新成因模式。渗滤熔体和岩石圈地幔之间的反应不仅导致了矿物含量的变化,而且形成了特征的微量元素配分型式和同位素组成。REE模拟计算表明,熔体／岩石比值的大小、熔体性质以及熔体-岩石反应机制的多样性是控制本区幔源包体地球化学及其岩石变形、结晶程度之间相关性的重要因素。     

广东长坑金银矿床成矿机制热力学模拟研究

长坑金银矿床为沉积岩中的微细浸染型金矿与交代型银矿构成的矿床组合,金、银矿化与碳酸盐和碎屑岩围岩的硅化蚀变关系密切并呈分带现象,矿石类型主要为含矿硅化岩。矿化温度主要在300～170 C之间,成矿流体的主要成分为K~-、Na~-、Ca~(2+)、Mg~(2+)、Cl~(-)。金属配合物的分配计算显示,金在成矿热液中主要以疏氢配合物迁移,而银、铁、铅、锌则以氯配合物为主,铁、铅、锌在成矿后期的中性-弱碱性环境下可转变为羟基和硫氢配合物。热液-碳酸盐岩反应模拟证实水-岩相互作用是银矿石形成的有效机制。矿物组合的溶解度分析表明,金、银矿物分别在早期弱酸性和后期中-碱性条件下沉淀富集,这是造成金、银矿体分离和分带的主要或有利因素。     

Mechanistic and Kinetic Study of the Gas-Phase Reaction of Atomic Chlorine with Cyclohexanone using an Absolute and a Relative Technique; Influence of Temperature

The reaction of Cl with cyclohexanone (1) was investigated, for the first time, as a function of temperature (273–333 K) and at a low total pressure (1 Torr) with helium as a carrier gas using a discharge flow-mass spectrometry technique (DF-MS). The resulting Arrhenius expression is proposed, k ₁= (7.7 ± 4.1) × 10^–10 exp[–(540 ± 169)/T]. We also report a mechanistic study with the quantitative determination of the products of the reaction of Cl with cyclohexanone. The absolute rate constant derived from this study at 1 Torr of total pressure and room temperature is (1.3 ± 0.2) × 10^–10 cm³ molecule^–1 s^–1. A yield of 0.94 ± 0.10 was found for the H-abstraction channel giving HCl. In relative studies, using a newly constructed relative rate system, the decay of cyclohexanone was followed by gas chromatography coupled with flame-ionisation detection. These relative measurements were performed at atmospheric pressure with synthetic air and room temperature. Rate constant measured using the relative method for reaction (1) is: (1.7 ± 0.3) × 10^–10 cm³ molecule^–1 s^–1. Finally, results and atmospheric implications are discussed and compared with the reactivity with OH radicals.     

工程场地土层地震反应模型实例分析

在给定基岩地震输入的情况下计算实际场地土层不同深处的地震动反应谱,然后修改实际土层模型参数,在考虑土层厚度和软弱夹层变化的情况下进行地震反应分析,得出一些有意义的结论。     

雄黄矿物表面氧化过程的量子化学计算

采用密度泛涵量子化学计算方法对雄黄矿物晶体{010}晶面进行了计算，分析了该晶面的表面化学反应活性，表明表面上不同位置As、S原子的化学活性相差不大；同时对雄黄矿物晶体{010}表面吸附H2O、O2分子时的模型进行了势能面扫描计算，发现H2O和O2分子在该表面吸附时将发生解离，同时雄黄中的As将被氧化而形成砷的氧化物。     

Reaction pathways and reaction progress for the smectite-to-chlorite transformation: evidence from hydrothermally altered metabasites

The transformation from smectite to chlorite has been interpreted as involving either a disequilibrium chlorite/smectite mixed‐layering sequence, or an equilibrated discontinuous sequence involving smectite–corrensite–chlorite. Here, analysis of the smectite to chlorite transition in different geothermal systems leads us to propose that the transformation proceeds via three contrasting reaction pathways involving (i) a continuous mixed‐layer chlorite/smectite series; (ii) a discontinuous smectite–corrensite–chlorite series and (iii) a direct smectite to chlorite transition. Such contrasting pathways are not in accord with an equilibrium mineral reaction series, suggesting that these pathways record kinetically controlled reaction progress. In the geothermal systems reviewed the style of reaction pathway and degree of reaction progress is closely correlated with intensity of recrystallization, and not to differences in thermal gradients or clay grain size. This suggests a kinetic effect linked to variation in fluid/rock ratios and/or a contrast between advective or diffusive fluid transport. The mode of fluid transport provides a means by which the rates of dissolution/nucleation/growth can control the reaction style and the reaction progress of the smectite to chlorite transition. Slow rates of growth are linked to the first reaction pathway involving mixed‐layering, while increasing rates of growth, relative to nucleation, promote the generation of more ordered structures and ultimately lead to the direct smectite to chlorite transition, representative of the third pathway.     

Diffusion-controlled growth of wollastonite rims between quartz and calcite: comparison between nature and experiment

Growth rates of wollastonite reaction rims between quartz and calcite were experimentally determined at 0.1 and 1 GPa and temperatures from 850 to 1200 °C. Rim growth follows a parabolic rate law indicating that this reaction is diffusion‐controlled. From the rate constants, the D′δ‐values of the rate‐limiting species were derived, i.e. the product of grain boundary diffusion coefficient D′ and the effective grain boundary width, δ. In dry runs at 0.1 GPa, wollastonite grew exclusively on quartz surfaces. From volume considerations it is inferred that (D′_CaOδ)/(D′_SiO2δ)≥1.33, and that SiO₂ diffusion controls rim growth. D′_SiO2δ increases from about 10^?25 to 10^?23 m³ s^?1 as temperature increases from 850 to 1000 °C, yielding an apparent activation energy of 330±36 kJ mol^?1. In runs at 1 GPa, performed in a piston‐cylinder apparatus, there were always small amounts of water present. Here, wollastonite rims always overgrew calcite. Rims around calcite grains in quartz matrix are porous and their growth rates are controlled by a complex diffusion‐advection mechanism. Rim growth on matrix calcite around quartz grains is controlled by grain boundary diffusion, but it is not clear whether CaO or SiO₂ diffusion is rate‐limiting. D′δ increases from about 10^?21 to 10^?20 m³ s^?1 as temperature increases from 1100 to 1200 °C. D′_SiO2δ or D′_CaOδ in rims on calcite is c. 10 times larger than D′_SiO2δ in dry rims at the same temperature. Growth structures of the experimentally produced rims are very similar to contact‐metamorphic wollastonite rims between metachert bands and limestone in the Bufa del Diente aureole, Mexico, whereby noninfiltrated metacherts correspond to dry and brine‐infiltrated metacherts to water‐bearing experiments. However, the observed diffusivities were 4 to 5 orders of magnitude larger during contact‐metamorphism as compared to our experimental results.     

CNO燃烧核反应的研究

本文利用势垒穿透模型计算重离子融合反应截面,我们发现理论计算结果同现有的实验数据符合得相当好。在此基础上,对~(12)C+~(12)C,~(12)C+~(14)N,~(12)C+~(16)O,~(14)N+~(14)N,~(14)N+~(16)O和~(16)O+~(16)O六种融合反应,在T_9=-0.1—5.0温度范内数值计算了这些热核反应率,并给出了它们随温度变化的近似解析表达式.对~(12)C+~(12)C,~(12)C+~(16)O和~(16)O+~(16)O这三种热核反应率,我们的新结果明显地低于Caughlan等人在1985年的列表值,特别是~(16)O+~(16)O的热核反应率比文[21中值低7—20倍,这将对整个大质量恒星的演化、超新星爆发以及核合成带来较大的影响,本文简略地讨论了这些影响.     

Sensitivity of a Titan ionospheric model to the ion-molecule reaction parameters

Various aspects of ion-molecule reactions for Titan ionospheric chemistry modeling are reviewed in this work: temperature/collision energy effects on reaction rates and, more importantly, on products distributions; differential reactivity of isomers of ions; reactivity of excited states of ions; pathways to the building of complex ions. We evaluate here the extent to which these points affect model predictions. We find that the present limiting factors to model predictivity are the model incompleteness for heavy ion production pathways; the differential reactivity of isomers; and, to a lesser degree, the temperature effects on the branching ratios of ion-molecule reactions. Extensive experimental studies are required to fill these gaps in ion-molecule reactivity knowledge.