等压法测定298.15K下LiCl-CaCl2-H2O体系的活度系数

电解质水溶液热力学性质的研究一直是一个很活跃的研究领域.对含锂水盐体系热力学性质的研究不仅对电解质水溶液理论,而且对盐湖锂资源的开放利用都有非常重要的意义.姚燕等对ＬｉＣｌＫＣｌＨ2Ｏ[1],ＬｉＣｌＭｇＣｌ2Ｈ2Ｏ[2],ＬｉＣｌＭｇＳＯ4Ｈ2Ｏ[3,4],ＬｉＣｌＬｉ2ＳＯ4Ｈ2Ｏ[5]体系多温下热力学性质进行了研究,应用Ｐｉｔｚｅｒ电解质水溶液理论模型进行处理,计算出ＬｉＣｌ在不同体系中,很大的浓度范围内的活度系数.但在盐湖卤水中,ＣａＣｌ2的存在很普遍.对ＬｉＣｌＣａＣｌ2混合物在水溶液中的热力学性质研究对理解ＬｉＣｌ在盐…     

电解质水溶液热力学性质计算

推荐了一种新的电解质水溶液热力学性质计算方法.利用文献数据对CaCl_2-H_2O,H_2SO_4-H_2O和H_2SO_4-CuSO_4-H_2O系溶质平均活度系数及水的活度在广泛的浓度范围内进行了验算.计算结果均与文献报导值相当一致.其中二元素的结果相对误差小于5%,三元素不超过16%.     

乙醇-环己烷体系中NaI活度系数的测定与计算

由于非水溶剂的应用日趋广泛,促使物理化学工作者对于溶剂和溶液性质进行研究,同时开展了有关物理化学数据的测定和积累工作,以利于指导实践[1]。目前文献报道含水混合溶剂中的电解质活度系数较多,但非水混合溶剂中电解质活度系数报道较少。电解质浓溶液活度系数的计算方法目前应用较广的是Pitzer半经验算法[2]。Pitzer的算法中具体物系的β(0)、β(1)等系数需从实测活度系数数据拟合求得。孙仁义等通过测定汽液平衡盐效应的方法研究了盐在混合溶剂中的活度系数[3-4]。最近孙仁义等[5]提出了双液比固定条件下含盐体系汽液平衡数据热力学一…     

水溶液中氯化铯与糖(D-葡萄糖、D-果糖和蔗糖)相互作用的热力学参数研究(298.15K)

用钾离子选择性电极为测量电极,氯离子选择性电极为参比电极,设计组成无液接电池,用于氯化铯-糖(葡萄糖、果糖及蔗糖)-水三元体系中组分之间弱相互作用的热力学性质研究.通过测量电池的电动势获得氯化铯在糖水溶液中的活度系数,根据Scatchard理论推测出糖在氯化铯水溶液中的活度系数.通过Mcmillan-Mayer理论将体系的过量热力学函数与溶液中溶质的相互作用参数相关联,获得氯化铯与糖在水溶液中相互作用的吉布斯自由能参数及盐效应常数.运用结构相互作用模型、糖的羟基水化效应及色散能理论,探讨体系中溶质-溶质、溶质-溶剂间的相互作用及糖的立体结构和金属离子体积对热力学参数的影响.     

钨酸钠水溶液的活度系数和渗透系数

在周期表第ⅥB族元素Cr、Mo、W六价含氧离子钠盐化合物中,钨酸盐及其在水溶液中的热力学性质是知道得最少的.钨酸钠在水溶液中的活度系数和渗透系数虽然有报道,但由于测量方法不同,给出的结果彼此相差较大.结合着无机盐水溶液热力学性质的研究,我们对钨酸钠在水溶液中的活度系数用等压法进行了测量,浓度范围从0.3到2.5mol·kg~(-1).     

盐-水体系溶解平衡计算的自由能最小化及溶度积方法

根据电解质溶液的基本物理化学原理和近代电解质溶液理论的Pitzer离子相互作用模型,通过计算浓电解质溶液的活度系数和水的活度,研究了盐-水体系溶解平衡的计算方法.结果表明,体系Gibbs自由能最小化方法是计算盐-水体系溶解平衡的一种有效方法,其计算结果与溶度积法一致.     

混合电解质中HCl热力学性质——HCl-C3H8O3-NaCl-H2O体系

活度系数;电动势;电极电势;无液接电池;混合电解质中HCl热力学性质——HCl-C3H8O3-NaCl-H2O体系     

金属溶剂萃取的热力学研究(Ⅶ)——2-乙基己基膦酸单(2-乙基己基)酯-硫酸钻-硫酸铜体系

本文提出了具有相同电荷的同号离子间作用力相等的假定, 简化了Pitzer的电解质溶液活度系数计算公式, 用此公式, 计算了H_2SO_4-CoSO_4-CuSO_4水相体系各单个离子活度系数以及水的渗透系数。本文还应用由作者提出的工作参考态法, 应用改进的Scatchard-Hildebrand模型计算了EHEHPA-CoSO_4-CuSO_4萃取体系中有机相各组分的活度系数以及萃取反应热力学平衡常数.     

广义渗透系数

本文将Bjerrum渗透系数概念推广到混合溶剂体系中,提出了广义渗透系数的概念及其一般定义式,并导出了广义渗透系数与电解质活度系数之间的相互关系式,从而可以借助于广义渗透系数较易实现混合溶剂体系中溶质与溶剂热力学性质之间的相互推算,同时,混合溶剂作为一个整体的非理想性亦可得到具体度量.因此引入广义渗透系数概念具有理论与实际意义.     

含氯化钠电解质水溶液体系热力学性质研究进展

总结了近几十年来含氯化钠电解质水溶液体系热力学性质的研究成果及其在盐湖、地下卤水、油田水和海盐制备等领域的应用,并对含钠水盐体系在不同温度下的热力学性质进行了总结,对于推动含钠水盐体系电解质溶液理论的发展和促进富盐湖卤水、地下卤水及海水的开发利用具有重要的意义。     

Clusters of hydrated methane sulfonic acid CH3SO3H.(H2O)n (n = 1-5): a theoretical study

Ab initio and density functional methods have been used to examine the structures and energetics of the hydrated clusters of methane sulfonic acid (MSA), CH3SO3H.(H2O)n (n = 1-5). For small clusters with one or two water molecules, the most stable clusters have strong cyclic hydrogen bonds between the proton of OH group in MSA and the water molecules. With three or more water molecules, the proton transfer from MSA to water becomes possible, forming ion-pair structures between CH3SO3- and H3O+ moieties. For MSA.(H2O)3, the energy difference between the most stable ion pair and neutral structures are less than 1 kJ/mol, thus coexistence of neutral and ion-pair isomers are expected. For larger clusters with four and five water molecules, the ion-pair isomers are more stable (>10 kJ/mol) than the neutral ones; thus, proton transfer takes place. The ion-pair clusters can have direct hydrogen bond between CH3SO3- and H3O+ or indirect one through water molecule. For MSA.(H2O)5, the energy difference between ion pairs with direct and indirect hydrogen bonds are less than 1 kJ/mol; namely, the charge separation and acid ionization is energetically possible. The calculated IR spectra of stable isomers of MSA.(H2O)n clusters clearly demonstrate the significant red shift of OH stretching of MSA and hydrogen-bonded OH stretching of water molecules as the size of cluster increases.     

Methanesulfinic acid reaction with OH: mechanism, rate constants, and atmospheric implications

The mechanism for the atmospheric oxidation of methanesulfinic acid (MSIA) has been studied. This is the first theoretical study of the reaction between MSIA and the OH radical. All the possible channels in this reaction have been studied theoretically, and their corresponding rate constants have been evaluated under the variational transition-state theory (VTST) formalism. Two different products can be formed: the CH3S(O)2 radical (which had been experimentally proposed as the only one), and sulfurous acid (H2SO3). The CH3S(O)2 radical can be formed directly or can form via an intermediate adduct, which yields to the radical through the elimination of a water molecule. For the first time, it is theoretically demonstrated that SO2 is formed in the addition channel of the DMS + OH reaction. The consequences of this result in the interpretation of the T-dependence of the SO4(2-)/MSA (methanesulfonic acid) quocient are analyzed. The competition between the unimolecular dissociation of the CH3S(O)2 radical and OH-addition to yield MSA is proposed as one of the possible multiple branching points (along the DMS + OH degradation scheme) influencing the T-dependence of the SO4(2-)/MSA relation.     

Direct sulfonation of methane to methanesulfonic acid with SO2 using Ca salts as promoters

Direct liquid-phase sulfonation of methane to methanesulfonic acid (MSA) with SO2 has been achieved in triflic acid using K2S2O8 as the oxidant and a small amount of a Ca salt as the promoter. The effects of reaction conditions on the conversion of SO2 to MSA were examined. Included were the influence of solvent acidity, reaction duration, reaction temperature, amount of K2S2O8, and composition and amount of promoters.     

Acidity function of methanesulfonic acid solutions in DMF

The acidity function of solutions of methanesulfonic acids (MSA) in DMF and H₂O were measured by the indicator method at 25 °C in the 0–100% concentration range. A higher ionizing activity of HCl complexes with DMF as compared to that of similar MSA complexes was established. The relative ionizing activity of MSA molecules, H₅O₂ ⁺ ions, and ion pairs between MSA and DMF was determined. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 1940–1943, October, 1999.     

Application of the MSA-based models in correlating the surface tension for single and mixed electrolyte solutions

Experimental values for surface tension of single and mixed electrolyte solutions were correlated using the models based on the perturbation theory. The Mean Spherical Approximation (MSA) model, coupled with the Ghotbi–Vera (GV) and the Mansoori et al. (BMCSL) equations of state, were used to correlate the experimental values of the surface tension. The results showed that the models can favourably correlate the experimental values for single electrolyte solutions. However, it was observed that the GV–MSA model can more accurately predict the surface tension for single electrolytes, especially at higher concentrations. Two different expressions for concentration dependency of cation hydrated diameters were used. Therefore, in terms of such dependency different forms of the models, i.e., GV–MSA1, GV–MSA2, BMCSL–MSA1 and BMCSL–MSA2 were introduced. It should be stated that the prediction of the surface tension for the mixed electrolyte solutions were made without introducing any new adjustable parameters. The results showed that GV–MSA2 model can predict more accurately the surface tension of electrolyte mixtures particularly at higher concentrations. Finally, the GV–MSA model was directly used to correlate the experimental results for the surface tension for both single and mixed electrolyte solutions with 2 and 4 adjustable parameters. The results showed that both of the models can accurately predict the experimental data of surface tension. These models can favourably fit and also, predict the surface tension of single electrolyte solutions with less than 1% average absolute relative deviation (AARD). The prediction capability of the proposed models is also acceptable for mixtures of electrolytes.     

Capabilities of HPLC with APEX-Q nebulisation ICP-MS and ESI MS/MS to compare selenium uptake and speciation of non-malignant with different B cell lymphoma lines

The formation of intracellular dimethylselenide (DMSe) as a product of exposure of non-malignant (PBMCs) and lymphoma (RL and DHL-4) cell lines to methylseleninic acid (MSA) at clinical levels is suggested here for the first time. This was achieved by analysis of cell lysates by HPLC coupled to ICP-MS via APEX-Q nebulisation, enabling limits of detection for target methyl-Se species which are up to 12-fold lower than those obtained with conventional nebulisation. Methyl-Se-glutathione (CH₃Se-SG), although detected in lysates of cells exposed to MSA, was found to be a reaction product of MSA with glutathione. This was confirmed by HPLC-ESI MS (MS) analysis of lysates of control cells (unexposed to Se) spiked with MSA. The MS/MS data obtained by collision-induced dissociation fragmentation of the ion m/z 402 (for [M+H]^{+ 80}Se) were consistent with the presence of CH₃Se-SG. Formation of DMSe was not detected by HPLC-ICP-MS in these spiked lysates, and it was found to require live cells in cell media containing MSA. Interestingly, the ratio of DMSe to CH₃Se-SG was significantly higher in lymphoma cells exposed to MSA in comparison to non-malignant cells. Moreover, maximum Se uptake levels in lymphoma cell lines seemed to be reached much earlier (after 10 min of MSA exposure) than in non-malignant cells. Finally, the GC-TOF-MS speciation data obtained for cell headspace suggested that the major Se species (dimethyldiselenide) appeared to be present in lymphoma cell headspace at significantly higher concentrations than in non-malignant cell headspace after only 10 min of exposure to MSA. Evidence for the presence of dimethylselenidesulfide in lymphoma cell headspace is also provided for the first time.     

Homogeneous Catalytic Hydrogenation of Amides to Amines

Hydrogenation of amides in the presence of [Ru(acac)₃] (acacH=2,4‐pentanedione), triphos [1,1,1‐tris‐ (diphenylphosphinomethyl)ethane] and methanesulfonic acid (MSA) produces secondary and tertiary amines with selectivities as high as 93 % provided that there is at least one aromatic ring on N. The system is also active for the synthesis of primary amines. In an attempt to probe the role of MSA and the mechanism of the reaction, a range of methanesulfonato complexes has been prepared from [Ru(acac)₃], triphos and MSA, or from reactions of [RuX(OAc)(triphos)] (X=H or OAc) or [RuH₂(CO)(triphos)] with MSA. Crystallographically characterised complexes include: [Ru(OAc‐κ¹O)₂(H₂O)(triphos)], [Ru(OAc‐κ²O,O′)(CH₃SO₃‐κ¹O)(triphos)], [Ru(CH₃SO₃‐κ¹O)₂(H₂O)(triphos)] and [Ru₂(μ‐CH₃SO₃)₃(triphos)₂][CH₃SO₃], whereas other complexes, such as [Ru(OAc‐κ¹O)(OAc‐κ²O,O′)(triphos)], [Ru(CH₃SO₃‐κ¹O)(CH₃SO₃‐κ²O,O′)(triphos)], H[Ru(CH₃SO₃‐κ¹O)₃(triphos)], [RuH(CH₃SO₃‐κ¹O)(CO)(triphos)] and [RuH(CH₃SO₃‐κ²O,O′)(triphos)] have been characterised spectroscopically. The interactions between these various complexes and their relevance to the catalytic reactions are discussed.     

Metaheuristics for multiple sequence alignment: A systematic review

The Multiple Sequence Alignment (MSA) is a key task in bioinformatics, because it is used in different important biological analysis, such as function and structure prediction of unknown proteins. There are several approaches to perform MSA and the use of metaheuristics stands out because of the search ability of these methods, which generally leads to good results in a reasonable amount of time. This paper presents a Systematic Literature Review (SLR) on metaheuristics for MSA, compiling relevant works published between 2014 and 2019. The results of our SLR show the constant interest in this subject, due to the several recent publications that use different metaheuristics to obtain more accurate alignments. Moreover, the final results of our SLR show a multi-objective and hybrid approaches trends, which generally leads these methods to achieve even better results. Thus, we show in this work how the use of metaheuristics to perform MSA still remains an important and promising open research field.     

利用ESR技术研究α-蒎烯,β-蒎烯光敏氧化反应机理

本文主要利用电子顺磁共振(ESR)自旋捕获技术研究9,10 二氰基蒽(DCA)敏化α-蒎烯(αP),β-蒎烯(βP)光氧化反应.提供了在乙腈中α-蒎烯和β-蒎烯的光氧化反应过程中存在超氧负离子基(O₂^-)和单重态氧(¹O₂)的直接证据;在四氯化碳溶剂中只捕获到¹O₂;在正己烷中没有捕获到O₂^-或¹O₂.ESR实验结果进一步证明在乙腈中光敏氧化反应的¹O₂可能来自O₂^-和反应底物α、β-蒎烯正离子自由基之间的电荷复合(CR).     

Stability of reduced molybdosilicic acids

The effect of reduction on the stability of molybdosilicic acids (MSA) has been investigated. It has been found that when two or more of the 12 Mo(VI) atoms in alpha or beta-MSA are reduced to Mo(V), the products are stable in alkaline medium. Also, beta-MSA reduced to this extent is stable at higher temperature and is not transformed into alpha-MSA. Solutions in which the apparent degree of reduction is less than 2 Mo(V) per MSA ion should be treated as a mixture of unreduced MSA and MSA reduced exactly to 2 Mo(V) per MSA ion. A mixture of unreduced MSA and MSA reduced to contain 4 Mo(V) per MSA ion is not a stable system. The yellow unreduced MSA is reduced by the reduced form to give the product with 2 Mo(V) per MSA ion. The consequences for determining silicon as MSA are given, as well as a method of obtaining pure beta-MSA from a mixture of alpha-MSA and beta-MSA.