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.

Linear free energy relationships between reaction rate constants and equilibrium constants of complex compounds——III. Kinetics and mechanisms of ternary complex formation between (5-X-1, 10-phenanthroline)copper(II) and threonine

The kinetics of ternary complex formation involving Cu(5-X-1, 10-phen) and threonine (CuAL, A=5-X-1, 10-phen; L=threonine or represented by O-N; X=NO_2, Cl, H, CH_3) has been studied by temperature-jump and stopped-flow methods. The formation rate constants, k_f(M^(-1).s^(-1)), for the complexation reaction, CuA + LCuAL, are as follows; X=NO_2, 8.68×10~8; X=Cl, 7.13×10~8; X=H, 6.12×10~8; X=CH_3, 5.42×10~8. The rate constants for zwitterion attack are nil within experimental error. It has been found that a linear free energy relationship exists between the stability(logK_(CuAL)^(CuA) of the complexes CuAL and log kf as follows: IogK_(CuAL)^(CuA)=0.13 + 0.83 logk_f, r=0.99. It suggested that the formation rate governed the stability of the ternary complexes. The rates of formation of the ternary complexes increased with decreasing electron-donating property of the substituents. A linear relationship was found to exist as expressed by the following equation: log(k_f^R/k_F^O) = 0.097σ, r=0.96. A mechanism involves a rapid equilibrium between CuA and L followed by a slow ring closure of L.

Thermodynamic model for equilibrium solubility of gibbsite in concentrated NaOH solutions

The thermodynamic properties of the most important NaOH-NaAI（OH）4-H20 system in Bayer process for alumina production were investigated. A theoretical model for calculating the equilibrium constant of gibbsite dissolved in sodium hydroxide solution was proposed. New Pitzer model parameters and mixing parameters for the system NaOH-NaAI（OH）4-H20 were yielded and tested in the temperature range of 298.15-373.15 K. The results show that the proposed model for calculating the equilibrium constant of gibbsite dissolution is applicable and accurate. The obtained Pitzer model parameters of β（0）（NaAl（OH）4）、β（1）（NaAl（OH）4）和CΦ（NaAl（OH）4）,Al（OH）4 for NaAI（OH）4, the binary mixing parameter of θ（OH-Al（OH）4-） with OH-, and the ternary mixing parameter of ψ（Na＋OH-Al（OH）4-） for AI（OH）4- with OH- and Na＋ are temperature-dependent. The prediction of the equilibrium solubility of gibbsite dissolved in sodium hydroxide solution was feasible in the temperature range of 298.15-373.15 K.

Overview of the detection methods for equilibrium dissociation constant KD of drug-receptor interaction

Drug-receptor interaction plays an important role in a series of biological effects, such as cell pro- liferation, immune response, tumor metastasis, and drug delivery. Therefore, the research on drug-re- ceptor interaction is growing rapidly. The equilibrium dissociation constant （KD） is the basic parameter to evaluate the binding property of the drug-receptor. Thus, a variety of analytical methods have been established to determine the KD values, including radioligand binding assay, surface plasmon resonance method, fluorescence energy resonance transfer method, affinity chromatography, and isothermal ti- tration calorimetry. With the invention and innovation of new technology and analysis method, there is a deep exploration and comprehension about drug-receptor interaction. This review discusses the differ- ent methods of determining the KD values, and analyzes the applicability and the characteristic of each analytical method. Conclusively, the aim is to provide the guidance for researchers to utilize the most appropriate analytical tool to determine the KD values.

EQUILIBRIUM OF Mg-S IN Ni MELTS

The equilibrium of Mg-S in Ni melt was studied by the method of vapour equilibrium in a sealed chamber.At 1530℃ the equilibrium constant of the reaction MgS_(s)=Mg_(Ni)+S_(Ni)and the activity interaction coefficient were determined as K_(MgS)=6.76×10^(-5)and e_S^(Mg)=-9.1.

Measurement and model of density,viscosity,and hydrogen sulfide solubility in ferric chloride/trioctylmethylammonium chloride ionic liquid

The density and viscosity of ferric chloride/trioctylmethylammonium chloride ionic liquid(rFeCl_(3)/[A336]Cl)with different molar ratios(r=0.1-0.8)of FeCl_(3) to[A336]Cl were measured at temperatures from 313.15 to 358.15 K and atmospheric pressure.The density and viscosity data were fitted by the relevant temperature variation equations,respectively.The variation of density and viscosity with temperature and r was obtained.The solubility of rFeCl_(3)/[A336]Cl to H_2S was measured at temperatures from 318.15 to 348.15 K and pressures from 0 to 150 kPa.The effects of temperature,pressure,and r on the solubility of H_(2)S were discussed.The reaction equilibrium thermodynamic model(RETM)was used to fit the H_(2)S solubility data,and the average relative error was less than 1.3%,indicating that the model can relate the solubility data well.And Henry's constant and chemical reaction equilibrium constant were obtained by the RETM fitting.The relationships of Henry's constant and chemical reaction equilibrium constant with temperature and r were analyzed.

General Relation Valid for Electrolytic Systems

A simple general relation P = Q + R + 1 between the number P of kinds of species, the number Q of charge and elemental/core balances and the number R of independent equilibrium constants is deduced, and its validity is confirmed for non-redox and redox electrolytic systems, of different degree of complexity.

Hydrogenation of Silicon Tetrachloride in Microwave Plasma

This study investigated the hydrogenation of silicon tetrachloride （SIC14） in microwave plasma. A new launcher of argon （Ar） and hydrogen （Ha） plasma was introduced to produce a non-thermodynamic equilibrium activation plasma. The plasma state exhibited a characteristic temperature related to the equilibrium constant, which was termed ＂Reactive Temperature＂ in this study. Thus, the hydrogenation of SIC14 in the plasma could easily be handled with high conversion ratio and very high selectivity to trichlorosilane （SiHC13）. The effects of SiC14/Ar and H2/Ar ratios on the conversion were also investigated using a mathematical model developed to determine the op- timum experimental parameters. The highest hydrogenation conversion ratio was produced at a H2/SiCl4 molar ratio of 1, with mixtures of SICl4 and H2 to Ar molar ratio of 1.2 to 1.4. In this plasma, the special system pressure and incident power were required for the highest energy efficiency of hydrogenating SIC14, while the optimum system pressure varies from 26.6 to 40 kPa depending on input power, and the optimum feed gas （He and SiCI4） molar en- ergy input was about 350 kJ. mo1-1.

Study on Kinetics for Desulfurization of Model Diesel

In this study,by means of the experiments for desulfurization of model diesel through oxidative extraction,the changes associated with the rate of desulfurization of diesel and the mechanism for oxidation of sulfides in diesel were explored. Through studying the mechanism for oxidation of sulfides and the principle of solvent extraction,the kinetic equation of desulfurization via oxidative extraction were determined. By means of the evaluation of model parameters and curve fitting,the reaction order between organic sulfide and sulfone,the intrinsic oxidation rate constant of organic sulfide and sulfone,and the equilibrium constant between sulfone in model diesel and extractive solvent were determined. The experimental values of the desulfurization rate and the theoretical values of the corresponding model equation had closely demonstrated that the desulfurization reaction rate had high accuracy. And the reaction kinetics could provide an important basis for diesel desulfurization process in the future.

Analytical Approach to Clusters in near Critical CO2

Clusters greatly influence thermophysical properties of near critical gases. The cluster structures of supercritical fluids in general and Carbon Dioxide especially are important for the advanced supercritical fluid technologies and analytics development. The paper extends to near critical densities the developed earlier methods to extract the clusters’ properties from Online Electronic Database of NIST on thermophysical properties of fluids. This Database contains a hidden knowledge of cluster fractions’ properties in real gases. The discovered earlier linear chain clusters dominate at intermediate densities. Their properties can be extrapolated to high density gases, thus opening the way to study large 3D clusters in near critical zone. The potential energy density of a gas, cleared from the chain clusters’ contribution, reflects only the 3D clusters’ characteristics. A series expansion of this value by the Monomer Fraction density discovers properties of n-particle 3D clusters. The paper demonstrates a discrete row of 3D clusters’ particle numbers and gives estimations for bond energies of these clusters.

THERMODYNAMICS OF Cu-Ce-I(I=Al,Si,Ti,Fe)LIQUID SOLUTIONS

The iso-activity of[Ce]of samples reached in multiple-hole-graphite crucibles by controlling the oxygen potential through the reaction 2[Ce]+3CO=Ce_(2)O_(3)+3C.Combining conjugate gradient method of solving ill-conditioned equations,the activity interaction coeffients between Ce and Al.Si,Ti and Fe alloying elements were determined.The equilibrium constant of the reaction 2[Ce]+3[O]=Ce_(2)O_(3)and the standard free energy of formation of Ce203 in liquid Cu were obtained at 1.200 C.

Calculation of thermal physical parameters of dissociated air by the dissociation degree method

The high temperature gas occurs behind shock or near the wall surface of vehicle in the hypersonic flight. As the temperature exceeds 2 000 K, 4 000 K, respectively, O2 and N2 molecules are successively dissociated. Because of variable components at dif- ferent temperatures and pressures, the dissociated air is no longer a perfect gas, In this paper, a new method is developed to calculate accurate thermal physical parameters with the dissociation degree providing the thermochemical equilibrium procedure. Based on the dissociation degree, it is concluded that few numbers of equations and the solutions are easily obtained. In addition, a set of formulas relating the parameter to the dissociation degree are set up four-species, O2 molecule The thermodynamic properties of dissociated air containing and N2 molecule, O atom and N atom, are studied with the new method, and the results are consistent with those with the traditional equilibrium constant method. It is shown that this method is reliable for solving thermal physical parameters easily and directly.

Theoretical Research on the Multi-channel Reaction Mechanism of CHF Radical with HNCO by Density Functional Theory

The reaction mechanism of CHF radical with HNCO was investigated by the B3LYP method of density functional theory （DFT）, while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products were calculated at the B3LYP/6-311＋＋G＊＊ level. In the temperature range of 100-2600 K, the statistical thermody- namics and Eyring transition state theory with Winger correction were used to study the thermodynamic and kinetic characters of the channel with low energy barrier. In addition, the analysis on the combining interaction between CHF radical and HNCO was performed by atom-in-molecules theory （AIM） and natural bond orbitals （NBO） analysis. The calculation results indicated that the reaction of CHF radical with HNCO had ten channels, and the channel of NH direct extraction （CHF ＋ HNCO→IM6→TS7→IM7→CHFNH ＋ CO） in singlet state was the main channel with low potential energy and high equilibrium constant and reaction rate constant. CHFNH and CO were the main products.

The missing hydrogen ion,part-1:Historical precedents vs.fundamental concepts

The purpose of this review and commentary was to provide an historical and evidence-based account of organic acids and the biochemical and organic chemistry evidence for why cells do not produce metabolites that are acids.The scientific study of acids has a long history dating to the 16th and 17th centuries,and the definition of an acid was proposed in 1884 as a molecule that when in an aqueous solution releases a hydrogen ion(H^(+)).There are three common ionizable functional groups for molecules classified as acids:1)the carboxyl group,2)the phos-phoryl group and 3)the amine group.The propensity by which a cation will associate or dissociate with a negatively charged atom is quantified by the equilibrium constant(K_(eq))of the dissociation constant(K_(d))of the ionization(K_(eq)=K_(d)),which for lactic acid(HLa)vs.lactate(La^(-))is expressed as:K_(eq)=K_(d)=[H^(+)][La^(-)]/[HLa]=4677.3514(ionic strength=0.01 Mol⋅L^(-1),T=25℃).The negative log10 of the dissociation pKd reveals the pH at which half of the molecules are ionized,which for HLa=3.67.Thus,knowing the pKd and the pH of the solution at question will reveal the extent of the ionization vs.acidification of molecules that are classified as acids.

Mechanism of phthalic acid collector in flotation separation of fluorite and rare earth

The mechanism of phthalic acid,a dicarboxylic acid collector,in flotation separation of fluorite and rare earth(RE)was studied in this paper.The experimental data of flotation show that phthalic acid,as the collector,can realize highly efficient separation of fluorite and rare earth under weakly acidic conditions.The adsorption mechanism of phthalic acid on the surface of fluorite and bastnaesite was analyzed in this paper by means of the zeta potential measurement,the Fourier transform infrared(FT-IR),the X-ray photoelectron spectroscopy(XPS)and the stability constant measurement of active metal ion and phthalic acid coo rdination complex.According to the zeta potential testing results,the surfaces of fluorite adsorb the collector phthalate ion with negative charge under weakly acidic conditions which,in turn,increases its electronegativity and results in the motion of its potential.After the reaction between phthalic acid and fluorite ores under weakly acidic conditions,the peak of the fluorite ores is found to have significant changes in the FT-IR results,indicating strong chemical adsorption on the surfaces of phthalic acid and fluorite ores.According to the XPS analysis,the peak of benzene ring of phthalic acid is as high as 2%on the surface of fluorite,while no obvious characteristic peak of benzene ring is found on the surface of bastnaesite.According to the pH potentiometric titration results,the stability constant Ktotal of calcium phthalate complex within the acid range is higher than the stability constant K’total of cerium phthalate complex,indicating that the complex generated between phthalic acid and Ca^(2+)is more stable than the complex generated between phthalic acid and Ce^(3+).The possible reason is that Ca^(2+),with the highest reticular density,plays a prevailing role in the octahedron structure of fluorite amidst the acidic media.As the active point of flotation,Ca^(2+)works with the carboxyl groups of the collector phthalic acid(-C=O-)to form polycyclic calcium phthalate complex.

Extraction of copper with p-tert-butyl-calixarenes

The extraction of copper with calixarenes was researched by comparing the results from calix[4]-, calix[6]- and calix[8]-arenes. The extraction ability increased as the order: calix [4]? calix[8]? calix[6]-arenes, with the binding ratio being 1:1. The extraction mechanism was also discussed, and its equation Cu(NH3)42+ +H2L(0)→KexCu(NH3)4L(0) +2H+ and the extraction equilbrium constants (Kex) for calix[6]- and calix[8]-arenes were obtained respectively.

Association Mechanism Between Propionic Acid and Trioctylamine

Tertiary amines dissolved in diluents are attractive extractants for recovery of carboxylic acids from dilute aqueous solutions. Quantitative Fourier transform infrared (FTIR) analysis of organic solutions containing various concentrations of trioctylamine (TOA), n octanol, and propionic acid was carried out, and liquid liquid equilibrium was investigated using TOA in n octanol as the solvent. The fraction of ion pair association between TOA and propionic acid in the organic phase was quantitatively determined by FTIR. The apparent reactive extraction equilibrium constant, K 11 , was calculated using the quantitative FTIR spectrum and the equilibrium data. The results show that the fraction of ion pair association depends on diluent concentration, complex dissolution for propionic acid, and association between TOA and propionic acid. The K 11 based on quantitative FTIR has the same loading trend as that from the equilibrium data.

Studies on extraction of In(Ⅲ) with 8-hydroxyquinoline

The equilibrium molalities of In3+ in extraction reaction: In3+(aq)+3HOx(org) = In(Ox)_3(org) + 3H+(aq) were measured at ionic strengths from 0.13 to 2.54 mol-kg~ (-1) in the aqueous phase containing Na2SO4 as the supporting electrolyte and at constant initial molality of extractant, HOx, in the organic phase at temperatures from 278.15 to 308.15 K, where HOx and Ox mean 8-hydroxy-quinoliue and its anion, respectively. The standard extraction constants K0 at various temperatures were obtained by two methods proposed in our previous paper.

Determining PPARg-ligand binding affinity using fluorescent assay with cis-parinaric acid as a probe

Upon the study of small-molecules binding to proteins, the traditional methods for calculating dissociation constants (Kd and Ki) have shortcomings in dealing with the single bind- ing site models. In this paper, two equations have been derived to solve this problem. These two equations are independent of the total concentration or initial degree of saturation of receptor and the activity of the competitive molecule. Through nonlinear fitting against these two equations, Kd value of a probe can be obtained by binding assay, and Ki value of a ligand can be obtained by competitive assay. Moreover, only the total concentrations of receptor([R]t), ligand([L]t) and probe([P]t) are required for the data fitting. In this work, Ki values of some typical ligands of PPARγ were successfully determined by use of our equations, among which the Ki value of PPARγ-LY171883 was reported for the first time.

EffectofElectroacupunctureonPulmonaryβ－AdrenoceptorinAllergicAsthmaGuinea－Pigs

Twenty four male guinea-pigs were randomly divided into 3 groups: Group A, allergic asthmaguinea-pigs prepared by peritoneal injection and spraying inhalation of albumin; Group B, allergic asthmaguinea-pigs treated with electroacupuncture through stimulating the acupoint Feishu (UB13 ) and Group C, thecontrol group. With[3H] -DHA as a radioligand, pulmonary adrenoceptor ( AC) in the 3 groups of guinea-pigs were detrermined by radioligand binding assay technique. The results showed that: ( 1 ) The maximumbinding volume of receptor ligand ( Bmax, fmol/mg prot. ) of pulmonary AC in Group A (123. 86 42. 91 )was significantly lower than that in group C (199 . 54 37. 03 , P< 0. 05) , while the difference between groupB ( 142. 00 42. 91 ) and group C was not significant ( P > 0. 05 ) . ( 2 ) The Kd ( nM) of pulmonary AC ingroup A, B and C were 5 . 10 1 . 39 , 6. 53 2 . 41 and 8. 72 2 . 02 respectively, and the differences amongthe three groups were not significant ( P >0. 05) . The results indicated that the decrease of the content anddysfunction of pulmonary AC in allergic asthma guinea-pigs might be regulated by electroacupuncture thera-py.