Determination of Formation Constants of Ce^(3+) Complexes by Fluorescence

Fluorescence of Ce 3+ (aq) is very strong and thoroughly quenched when Ce 3+ forms complexes with ligands containing carboxylate or phosphate groups. This property is employed to develop a new simple method to determine formation constants of Ce 3+ complex system. Fluorescence intensity is used to determine concentration of Ce 3+ (aq) in complex solution, as it is proportional to the concentration of Ce 3+ (aq). In this paper, two examples, Ce 3+ malonic acid and Ce 3+ AMP(adenosine 5′ monophosphate), of fluorescence titration were made and association constants and association numbers of the two systems were deduced for the titration with Scatchard plot. The results are similar to those obtained by others. It is suggested that this Ce 3+ method is a promising fluorescence probe, as it is not only simple but also superior to other lanthanide fluorescence probe in being able to study a large amount of organic ligands and biomolecules.

Determination of Formation Constants of Co^2＋,Ni^2＋,Cu^2＋and Zn^2＋ Complexes with Humic and Fulvic Acids by Potentionmetric Titration Method

The formation constants of Co^2+,Ni^2+,Cu^2+ and Zn^2+ complexes with humic acid(HA) and fulvic acid(FA) in red soil wrer determined by the potentiometric titration method.The constants as a function of composition of the complexation solutions were obtained by two graphical approaches respetively,The formation constants decreased with increasing concentration of metal in the solution,The results provide unambiguous evidence for the heterogeneity of the function groups of humic substances,the formation constants of FA were much smaller than those of HA,and the formation constants of Cu^2+ were much greater than those of Co^2+ ,Ni^2+ and Zn^2+,The potentiometric titration methon for determining formation constants are also discussed in the article.

Determination of Apparent Formation Constants of Eu(III) with Humic Substances by Ion Selective Liquid Membrane Electrode

This is the novel measurement of the apparent formation constants of trivalent lanthanide with humic substances by potentiometric titration using an ion selective electrode (ISE) consisting of bis(diphenylphosphoryl)methane as an ionophore. The ISE prepared exhibited a Nernstian response to the Eu3+ concentration in the test solutions in the presence of humic acid and fulvic acid. The effect of the solution conditions, including the pH, initial metal and humic substance concentrations, and ionic strength, on the formation constants was examined. The present formation constants were compared with the reported data using solvent extraction method.

Study of Complex Formation Constants for Some Cations With O-Phenylenediamine in Binary Systems Using Square Wave Polarography Technique

The formation of metal cation complexes between o-phenylenediamine with metal ions, Ni2+, Cu2+, Zn2+, Pb2+ and Cr3+ were studied in the dimethylformamide/water(DMF/H2O), acetonitrile/water(AN/H2O) and ethanol/water(EtOH/H2O) binary systems using square wave polarography (SWP) technique. The stoichiometry and stability of the complexes were determined by monitoring the shifts in half-waves or peak potentials of the polarographic waves of metal ions against the ligand concentration. In the most cases, the formation constants of complexes decreased with increasing amounts of H2O, DMF and EtOH in AN/H2O, DMF/H2O and EtOH/H2O binary systems, respectively. The stoichiometry of the complexes was found 1:1. The results obtained show that there is an inverse relationship between the formation constant of the complexes and the donor number of the solvents based on the Gatmann donocity scale. Also, the stability constants show a high sensitivity to the composition of the mixed solvent systems. In most of the systems investigated, Cr3+ cation forms a more stable complex with o-phenylenediamine than other four cations and the order of selectivity of this ligand for cations in pure water is:Cr3+>>Cu2+>Ni2+>Zn2+>Pb2+.

The Quantum Scattering Study for Ion-pair Formation Reaction Na+I_2→Na^+I_2^- with the LCAC-SW method

The selected-state probabilities of collinear ion-pair formation process Na+I2→Na++I2-on Aten-Laming-Los two-State potential energy surface have been calculated by using LCAC-SW method. The results show that reaction probabilities are oscillatory with collision energy; the threshold energy of this ioniZation reaction is 2.8 ev, which is in modest agreement with experimental result.

Theoretical Study on the Ion-pair Formation Mechanism for the Li+I_2 →Li^+ + I_2^- System

For the Li + I2 →Li+ + I2- system, theoretical study has been performed on the QCISD(T) level by using the ab initio method. The collision complex in ion-pair formation process was found and optimized. These results show that the crossed molecule beam (CMB) experimental phenomenon is verified and the detailed geometry is given for the first time. A mechanism for ion-pair formation was proposed in detail. The position where the collision complex occurs affects the reaction path. Specifically, the process has threshold when the collision complex appeared before the crossing point between the covalent and ionic state potential energy surfaces. On the contrary, the process has no threshold after the crossing point. Theoretically, the title system belongs to the former case.

Formation and Role of H_2O_2 During Ozonation of Nitrobenzene

To better understand the formation of H2O2 in the ozonation of nitrobenzene and its role for the oxidation,a batch reactor of nitrobenzene ozonation was set up.The variables such as pH value,ozone dosage,and the presence of hydroxyl radical scavenger were investigated.The results showed that high accumulations of H2O2 were generally formed at low pH values and low ozone dosages.Moreover,H2O2 mainly formed after nitrobenzene was oxidized by hydroxyl radical during ozonation of the intermediates,such as p-nitrophenol,which reacted with ozone quickly in water.A small amount of additional H2O2 enhanced the nitrobenzene removal slightly.The kinetic study showed that nitrobenzene degradation fitted with pseudo-second-order kinetics well in the experiment.The kinetic constant values correlated linearly with the concentrations of H2O2 added.Thus,it is expected that the H2O2 formed in oxidation of nitrobenzene may initiate ozone decomposition to form hydroxyl radical and finally enhance the degradation of aromatic compounds to a certain extent.

Investigation of Iron Complex Formation of Anti-Hypertensive Drug: Methyldopa

The drug administered for any disease may play an unwanted function in biological system. They may have multiple counter effects, one of which is their interaction to bioactive metals. Iron is most common bio essential metal and is reported to interact with antihypertensive drug methyldopa. In the present study, above said complex is analyzed by UV-Visible spectrophotometry. Formation constant of the complex is calculated by using mole ratio method and single point statistical method which is in the range of 1010, values are also calculated which are independent of pH like formation constant. Absorbance maxima were found to be dependent on pH. At lower pH complex shows two broad bands centered at 430 nm and 730 nm. With the rise in pH later peak shifts toward lower wavelength, so 615 nm is selected for further studies. Molar extinction coefficient of the complex is explored by serial dilution method. At all wavelengths it increases with increase in pH. Mole ratio and slope ratio methods are used for exploring stoichiometry. Metal to ligand combining ratio in the complex is 1:2 at pH 4.0 and pH 4.5 while 1:3 at pH 5.0 and pH 5.5.

A Potentiometric Evaluation of Stability Constants of Two-Step Overlapping Equilibria via a Bilogarithmic Hyperbolic Cosine Method

A bilogarithmic hyperbolic cosine method for the evaluation of overlapping formation constants at varying (or fixed) ionic strength is devised in this paper and applied to data reported in the analytical literature, i.e. succinic acid system, Cu(II)-glycine system and Ag(I)-aminobutan-1-ol system. The method is based on the linearization of the formation function ? = f(pH) or ? = f(pL) data. A theoretical slope of unity should be obtained thus proving the correctness of the assumed equilibria. An additional advantage of the bilogarithmic method proposed is that it provides a closed scale representation of Y and X unlike other plots. This paper forms part of an investigation into the uses of bilogarithmic methods and hyperbolic functions in parameter estimation. Methods based on the application of spectrophotometric measurements have been the subject of recent studies.

Standard Molar Enthalpy of Formation of RE(C_5H_8NS_2)_3(C_(12)H_8N_2)

Four solid ternary complexes of RE (C_5H_8NS_2)_3(C_(12)H_8N_2) (RE=Eu, Gd, Tb, Dy) were synthesized in absolute ethanol by rare earth chloride low hydrate with the mixed ligands of ammonium pyrrolidinedi-thiocarbamate (APDC) and 1, 10-phenanthroline·H_2O (o-phen·H_2O) in the ordinary laboratory atmosphere without any cautions against moisture or air sensitivity. IR spectra of the complexes show that the RE^(3+) coordinated with six sulfur atoms of three PDC^- and two nitrogen atoms of o-phen·H_2O. It was assumed that the coordination number of RE^(3+) is eight. The constant-volume combustion energies of the complexes, Δ_cU, were determined as (-16937 88±9 79 ), (-17588 79±8 62 ), ((-17747 14±)8 25 ) and (-17840 37±8 87 ) kJ·mol^(-1), by a precise rotating-bomb calorimeter at 298.15 K. Its standard molar enthalpies of combustion, Δ_cH~θ_m, and standard molar enthalpies of formation, Δ_fH~θ_m, were calculated as (-16953 37±9 79), (-17604 28±8 62), (-17762 63±8 25), (-17855 86±8 87) kJ·mol^(-1) and (-857.04±10.52), (-282.43±9.58), (-130.08±9.13), (-55.75±9.83) kJ·mol^(-1).

Low-temperature heat capacities and standard molar enthalpy of formation of N-methylnorephedrine C11H17NO（s）

This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO（s） relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.

基于井筒-地层定压实验的重力置换窗口研究

为了处理重力置换引起的溢漏事故,首先需要了解重力置换发生的条件,分析重力置换窗口,判断井下是否发生重力置换,并采取对应的处理方法。通过自主研制的井筒-地层重力置换实验装置,开展气液、液液重力置换临界点实验,基于理论及实验分析,定量计算地层重力置换窗口,并拟合了重力置换窗口临界点压力曲线,拟合公式与实测值误差小于10%。在该实验条件下,当钻井液密度为0.998 g/cm3时,气液重力置换窗口为-5 800~10.6 Pa,液液地层重力置换的窗口为-1 192~16.6 Pa。结果表明,气液、液液重力置换窗口与流体密度差基本呈线性关系;现场实际井下重力置换窗口远高于此,所以需要在钻进时考虑重力置换窗口的影响。据此,提出了预防重力置换发生的方法,以及发生重力置换溢漏事故后对应的处理方法。

Chemical equilibrium constants of rare earth nitrates and tri-n-butyl phosphate complex formation

Mixed rare earth nitrates （REi（NO3）3） in the aqueous solution was mixed with tri-n-butyl phosphate （TBP, （n-C4H9O）3PO） dissolved in kerosene for the formation of their corresponding complexes （REi（NO3）3·ni（n-C4H9O）3PO） at 303 K. The effects of initial concentrations of both TBP and mixed rare earth nitrates on the equilibrium constants of their complex formations were investigated. The complexes were formed almost immediately after mixing. The simultaneous formations reached their chemical equilibria within a few minutes by shaking the mixture at 200 r/min. The chemical equilibrium constants of the complex formations were independent of the initial TBP concentrations. However, they were decreased by reducing the concentration of REi（NO3）3. All equilibrium constants of the simultaneous complex formations were less than 0.7, while the average molar ratio of TBP to REi（NO3）3 of the complexes varied between 1.0 and 1.6. The chemical equilibrium constant for the formation of La（NO3）3·（n-C4H9O）3PO was 0.09, while that of Dy（NO3）3·（n-C4H9O）3PO was 0.68. The ascending sequence of chemical equilibrium constants for the simultaneous formations was La, Ce, Pr, Nd, Eu, Y, Sm, Gd, and Dy.

New Mechanism and Analytical Formula for Understanding the Gravity Constant <i>G</i>

The nature of gravitation and G is not well understood. A new gravitation mechanism is proposed that explains the origin and essence of the gravitational constant, G. Based on general relativity, the vacuum is considered to be a superfluid with measurable density. Rotating bodies drag vacuum and create a vortex with gradient pressure. The drag force of vacuum fluid flow in the arm of the vortex is calculated relative to the static vacuum and a value that is numerically equal to that of G is obtained. Using Archimedes’ principle, it is determined that G is the volume of vacuum displaced by a force equivalent to its weight which is equal to the drag force of the vacuum. It is concluded that the gravitational constant G expresses the force needed to displace a cubic metre of vacuum that weighs one kg in one second. Therefore, G is not a fundamental physical constant but rather is an expression of the resistance encountered by the gravitational force in the vacuum.

陆相混积型页岩储集层孔隙结构特征及其控制因素

陆相混合沉积岩岩性复杂,储集层物性差异大,其孔隙结构及其主控因素,是揭示陆相混积型页岩储集层物性的关键。通过岩石薄片、铸体薄片、扫描电镜、高压压汞、恒速压汞、X射线衍射等,识别了吉木萨尔凹陷二叠系芦草沟组页岩储集层岩性,分析了不同岩性的孔隙结构特征及其与成岩作用的关系。芦草沟组页岩储集层主要发育泥晶白云岩、粉砂质砂屑白云岩、石灰质粉砂岩、石灰质泥岩、粉砂质凝灰岩和石灰质凝灰岩6种岩性。粉砂质砂屑白云岩、石灰质粉砂岩和粉砂质凝灰岩压实程度中等,溶蚀孔发育,孔喉半径大,孔隙连通性及孔喉分选好,储集层物性好;石灰质凝灰岩压实作用中等,主要以方解石、自生石英及方沸石胶结为主,储集层物性中等;泥晶白云岩和石灰质泥岩成分单一,压实作用较强,溶蚀作用弱,孔喉半径小,物性差。

定容气藏水平井停喷原因判识方法及应用

水平气井停喷是定容气藏开发中后期面临的普遍问题,需要及时判识停喷原因并采取生产恢复措施。为此,将水平井临界携液理论方程与水平井二项式产能方程、井底流压计算方程相结合,建立临界携液流量、临界举升压差、临界地层压力3个停喷判据,分析井口压力、油管内径等因素对判据的影响,研究3个判据在气井停喷原因判识中的作用,并创建了快速判识水平井停喷原因的方法。研究表明:临界携液流量与井口压力和油管内径均呈乘幂函数递增关系,井口压力越高、油管内径越大,临界携液流量越大,当气井实际气量低于临界携液流量时,即可判定井筒已开始积液;临界举升压差与油管内径无关,只随井口压力呈线性上升,当实际举升压差低于临界举升压差时,需考虑气井举升液体动力不足的问题;油管内径保持不变时,临界地层压力随井口压力呈线性上升,在地层压力消耗较大的情况下,临界地层压力易超出气井实际地层压力,即气井会因驱动能量不足而引发停喷。应用实例证明,该方法能够有效判识水平气井停喷原因,为工艺措施提供理论依据。该方法的建立对于定容气藏低压阶段的高效开发具有重要指导意义。

双星InSAR时间同步误差对相位同步的影响

针对双星编队的InSAR雷达系统,提出了SAR与相位同步一体化的系统框架,在双星时间同步误差的基础上,提出了一种综合考虑时间同步误差、SAR和相位同步发射及接收链路时延的双星相位同步设计方法,给出了相位同步补偿后的辅星回波信号相位和双星干涉相位,推导了两种时变相位误差功率谱密度,经过理论分析和仿真试验证明:相位同步补偿后,时间同步误差不影响相位同步精度,只影响辅星目标位置。辅星回波固定相位误差较大,但不影响成像,双星干涉固定相位误差为千分之几度,对干涉测高精度影响可以忽略,辅星回波和双星干涉时变相位误差与主星相近。

Nonadiabatic collision model calculations of ion-pair formation cross sections of Cs+O2→Cs++O2-

This paper has improved Hickman's nonadiabatic collision model by substituting Hickman's constant velocity classical straight line trajectory approximation with the solution of motion equation mR=-dV(R)/dR, and has calculated the cross sections of ion-pair formation Cs+O2 -Cs++O2- with the improved nonadiabatic collision model (INCM). A comparison of our results with other theoretical and experimental results has been made.

L-苏糖酸与金属离子的配位性能

本文在２９８Ｋ、Ｉ＝０．１ｍｏｌ·Ｌ－１ＫＮＯ３条件下测定了Ｌ－苏糖酸的质子化常数及其与钙（Ⅱ）、镉（Ⅱ）、锌（Ⅱ）、钴（Ⅱ）、铜（Ⅱ）二元配合物的生成常数。Ｌ－苏糖酸的质子化常数与葡萄糖酸的质子化常数一致，ｐＫａ为３．５６。其与金属离子的配位方式也与葡萄糖酸一致，但其二元配合物的生成常数明显比葡萄糖酸大。Ｌ－苏糖酸与不同金属离子作用的方式不同，与钙（Ⅱ）、镉（Ⅱ）、锌（Ⅱ）、钴（Ⅱ）配位时不解离出醇羟基质子，而与铜（Ⅱ）配位时则解离出醇羟基质子而形成螯合物。形成螯合物时醇羟基的ｐＫａ为６．０７。配合物生成常数的对数分别为：钙（Ⅱ），１．７４（１１０）；镉（Ⅱ），４．６３（１２０）；锌（Ⅱ），２．００（１１０）；钴（Ⅱ），２．２９（１１０）；铜（Ⅱ），３．６５（１１０）、－２．４２（１１－１）、－５．４１（１２－２）。不同金属离子配合物生成常数的大小符合Ｉｒｖｉｎｇ－Ｗｉｌｉａｍ序列。本文结果在一定程度上支持了分子补钙的假说。

β－环糊精与萘普生在水溶液中的包合作用

研究了萘普生（ｎａｐｒｏｘｅｎ，Ｎａｐ）在不同温度，不同浓度β－环糊精β－ｃｙｃｌｏｄｅｘｔｒｉｎ，β－ＣＤ）水溶液中的溶解度及其热力学参数，测定紫外吸收光谱变化值（△Ａ），用连续递变法测定包合物组成的摩尔比．实验证明，蔡普生在β－ＣＤ水溶液中的溶解度曲线呈ＡＬ型，包合物组成摩尔比为１：１．温度升高，Ｎａｐ·β－ＣＤ包合物的结合常数（Ｋｃ）减小，包合物生成能（△Ｇ）Ｊ曾大，反应热（△Ｈ）为－２．９２（ＫＪ／ｍｏｌ），包合过程为放热过程。