Solvent effect on standard electrode potential: Part III. Silver-silver chloride electrode in methanol-water mixtures

From measurements of the electromotive force of the Pt, H₂ (gas, 1 atm); HCl (m), X% methanol, Y% water; AgCl, Ag cells at nine temperatures from 15 to 55°C at 5° intervals, the standard potential of the silver-silver chloride electrode has been determined over a broad range of methanol concentrations (0–90 wt. % methanol). The standard molal potential in the various solvent mixtures has been expressed as a function of temperature. The primary medium effects of various media on hydrochloric acid, and the standard thermodynamic quantities accompanying the transfer of HCl from water to the respective solvent media have been computed. The results have been discussed both in terms of the acid-base behaviour of the solvent mixtures and also their structural effects on the transfer process.     

Solvent effect on standard electrode potential: Part V. Silver-silver chloride electrode in tert-butyl alcohol + water mixtures

The electromotive force measurements of the cell Pt, H₂ (gas, 1 atm); HCl (m), X % Bu ^tOH, Y% H₂O; AgCl, Ag, at nine different temperatures ranging from 15 to 55°C at 5° intervals, have been used to determine the standard potentials of the silver-silver chloride electrode in eighteen tert-butyl alcohol+water solvent mixtures containing up to 90 wt. % alcohol. The standard molal potentials in each solvent have been represented as a function of temperature. The standard thermodynamic functions for the cell reaction, the primary medium effects of various solvents upon HCl, and the standard thermodynamic quantities for the transfer of one mole of HCl from water to tert-butyl alcohol+water media have been evaluated. The results have been discussed in the light of ion-solvent interactions as well as the structural changes of the solvents.     

Thermodynamics of hydrochloric acid in (1-propanol+water) from electromotive-force measurements

The standard electromotive force of the cell: PtH₂(g)|HCl(m) in solvent |AgCl|Ag has been determined at 9 different temperatures ranging from 288.15 to 328.15 K in 20 (propan-1-ol+water) mixtures covering the whole range of solvent composition, by an extrapolation method making use of the extended terms of the Debye-Hückel theory. In solvents of high alcohol content, where the dielectric constant is small, it was necessary to correct for ion-pair formation. The temperature variation of the standard e.m.f. was used to calculate the standard thermodynamic functions for the cell reaction, the primary medium effects of various solvents upon HCl, and the standard quantities for the transfer of HCl from the standard state in water to the standard states in each other solvent. The significance of the transfer functions is discussed in relation to the acid-base strength, as well as the structural features of the solvents.     

Thermodynamics of silver—silver halide electrodes and thermodynamic solubility products of silver halides in glycerol + water mixtures at different temperatures

The standard potentials of silver—silver bromide and silver—silver iodide electrodes in glycerol+water mixtures containing 5, 10, 20 and 30 wt% glycerol were determined from electromotive force measurements of the cell Ag(s), AgX(s), KX(c)//KCl(c), AgCl(s), Ag(s), where X is Br or I, at seven different temperatures in the range 5–35°C. The standard potentials in each solvent are represented as a function of temperature. The standard thermodynamic functions for the electrode reactions, the primary medium effects of various solvents upon X⁻, and the standard thermodynamic quantities for the transfer of 1 g-ion of X⁻ from water to the respective glycerol + water media are evaluated and discussed in the light of ion—solvent interactions as well as the structural changes of the solvents. From the values of the Ag/Ag⁺ and Ag/AgX, X⁻ electrodes, the thermodynamic solubility product constants of silver chloride, silver bromide and silver iodide have been determined in glycerol + water solvent mixtures at different temperatures.     

Standard potentials of silver-silver bromide electrode and related thermodynamic quantities in (5, 10 and 15 wt-%) 2-butanol-water mixtures

The standard potentials of silver-silver bromide electrode in 5, 10 and 15 wt.-% 2-butanol have been determined from e.m.f. measurements of a cell of the type: Pt(or Pd), H₂(g)|HBr(m), 2-butanol-water mixtures| AgBr, Ag at temperatures 15°, 25° and 35°C and in the molality range of HBr from 0.003 to 0.1 mol kg^?1. Standard potentials were utilized to calculate: (1) the standard thermodynamic quantities for the cell reaction and for the reaction of HBr formation, (2) the mean activity coefficients of HBr, and (3) the standard thermodynamic quantities for transfer of HBr from water to 2-butanol-water mixtures. The thermodynamic functions for the transfer process have been interpreted in regard to the acid-base properties and structure of the solvents.     

Thermodynamic studies of hydriodic acid in ethylene glycol-water mixtures from electromotive force measurements

The standard potentials of the Ag—AgI electrode in twenty ethylene glycol—water mixtures covering the whole range of solvent composition have been determined from the e.m.f. measurements of the cell Pt¦H₂(g, 1 atm)¦HOAc (m ₁), NaOAc (m ₂), KI(m ₃), solvent¦AgI¦Ag at nine different temperatures ranging from 15 to 55°C. The temperature variation of the standard e.m.f. has been utilized to compute the standard thermodynamic functions for the cell reaction, the primary medium effects of various solvents upon HI, and the standard thermodynamic quantities for the transfer of HI from the standard state in water to the standard states in the respective solvent media. The chemical effects of solvents on the transfer process have been obtained by subtracting the electrostatic contributions from the total transfer quantities. The results have been discussed in the light of ion—solvent interactions as well as the structural changes of the solvents.     

Thermodynamic properties of the silver ion in alcohol + water solvent mixtures from electromotive force measurements and thermodynamic solubility product constants of AgX (X = Cl,Br, I or CNS) at different temperatures

The standard potentials of the silver-silver ion electrode in alcohol+water solvent mixtures containing 10 and 20 wt% methanol, ethanol, 1-propanol and 2-propanol have been determined from the electromotive force measurements of the cell Ag(s), AgCl(s), NaCl(c), NaNO₃(c)// NaNO₃(c), AgNO₃(c), Ag(s) at seven different temperatures in the range 5–35°C. The standard potentials in each solvent have been represented as a function of temperature. The standard thermodynamic functions for the electrode reaction, the primary medium effects of various solvents upon Ag⁺, and the standard thermodynamic quantities for the transfer of 1 g-ion of Ag⁺ from water to the respective alcohol + water media have been evaluated and discussed in the light of ion-solvent interactions as well as the structural changes of the solvents. From the values of the standard potentials of the Ag/Ag⁺ and Ag/AgX, X^? electrodes, the thermodynamic solubility product constants of silver chloride, silver bromide, silver iodide and silver thiocyanate have been determined in alcohol + water solvent mixtures at different temperatures.     

Absolute electrode potential and thermodynamics of single ions

A new method, relating the electrode potential to the radius of the solvated ion on whose activity the potential depends, has been developed for the determination of absolute electrode potentials and the thermodynamics of single ions in solution. It is successfully applied to the cells: Pt|H₂(g, 1 atm)|HX, solvent |AgX|Ag, and M|MX, solvent|AgX|Ag, in aqueous, partially aqueous, and non-aqueous solvents. The absolute electrode potentials have been computed in aqueous and methanol+water solvents. The single ion activities, activity coefficients, the radii of solvated cations, and their solvation extent have been calculated. The temperature variation of the standard absolute potential has been utilized to evaluate the standard thermodynamic functions for the electrode reactions, and the standard transfer thermodynamic quantities of single ions from water to methanolic solvents. The results are interpreted in terms of ion—solvent interactions as well as the structural features and the acid—base properties of these solvents.     

Influence of Glycerol and Temperature on the Phase Behavior and Micellization of CTAB and SDS in Aqueous Solutions

In this work the micellization of sodium dodecylsulfate (SDS) and cetyltrimethyammonium bromide (CTAB) in water-glycerol mixed solvent have been investigated at 25, 35, and 45°C, respectively. The micellization of both surfactants in pure water at different temperatures has also been studied. The phase diagrams of the surfactants in water-glycerol mixed solvent were also established. From the conductivity measurements, the critical micelle concentration (CMC) and the degree of counterion dissociation (β) were obtained as a function of glycerol-water ratio and temperature. Standard free energy of micellization (ΔG°_mic) as a function of glycerol contents and temperature was calculated and discussed. It has been found that the micellization of the two surfactant in solutions with glycerol at 25°C and in pure water at higher temperatures are not the same although they have equal dielectric constants values.     

Thermodynamics of the silver—silver thiocyanate electrode in urea—water mixtures

E.m.f. measurements on cells of the type Ag(s), AgCNS(s), KCNS(c)//KCl(c), AgCl(s), Ag(s) in four different composition of urea—water mixtures at seven different temperatures from 5 to 35°C have been made to determine the standard potentials of the silver—silver thiocyanate electrode in these media. These values have been used to evaluate the transfer thermodynamic quantities accompanying the transfer of 1 g ion of CNS^? ion from the standard state in water to the standard state in urea—water mixtures.     

HCl-NaCl-C3H8O3-H2O体系溶液热力学性质

在恒定丙三醇质量分数x=0．1的条件下，测定了无液接电池（A）和电池（B）的电动势根据电池（A）电动势确定了丙三醇和水混合溶剂中的Ag－AgCl电极的标准电极电势，讨论了HCl的迁移性质；由电池（B）测得的电动势计算了HCl在该体系中的活度系数γA，计算的结果表明，对于所讨论的体系，在溶液中总离子强度保持恒定，HCl的活度系数服从Harned规则．在溶液组成恒定时，IgγA是温度倒数1／T的线性函数，讨论了混合物中HCl的相对偏摩尔焓及介质效应．     

Evaluation of the Standard Potential of the Ag/AgCl Electrode in a 50 wt-% Water–Ethanol Mixture

This paper deals with the evaluation of the standard potential of the Ag/AgCl electrode in a water–ethanol mixture (50 wt-%). A potentiometric method was applied using a cell without liquid junction. Mean activity coefficients of HCl in the same mixture have been also determined. The measurements were performed in the HCl molality range from 0.005 to 0.1 mol⋅kg⁻¹. The Debye–Hückel theory and Pitzer’s model, based on the interactions present in the solution, have been applied. Good agreement was found between the results obtained with the two approaches. Uncertainties of the Pitzer parameters and interionic forces are discussed based on the values found. The variation of the standard potential as a function of the temperature was used to calculate the transfer thermodynamic functions. The effects of the solvent composition on the thermodynamic properties of HCl allow to highlight structural changes in water–ethanol mixtures.     

Relaxation dynamics in glycerol-water mixtures. 2. Mesoscopic feature in water rich mixtures

The relaxation dynamics of water-rich glycerol-water mixtures is studied by broadband dielectric spectroscopy (BDS) at 173-323 K and differential scanning calorimetry (DSC) at 138-313 K. These data indicate the existence of the critical concentration of 40 mol % glycerol. In the studied temperature range for water-rich glycerol mixtures, the two states of water (ice and interfacial water) are observed in addition to water in the mesoscopic 40 mol % glycerol-water domains. The possible kinetics of water exchange between different water states is discussed in order to explain the mechanism of the broad melting behavior observed by DSC.     

Heterocyclic hydroxamic acids. V. Thermodynamics of the interaction of some bivalent metal ions with N-phenyl-2-furohydroxamic acid and its analogues

In recent years, considerable effort has been devoted to physico-chemical studies in non-aqueous and mixed solvents. Most of these have been concerned with solutions in mixed solvents with a view to explaining the effect of a changing solvent composition of the ion—solvent and electrode—solvent interactions. Several workers [1–6] have presented studies of electrode—solvent interactions in water—dioxane, water—glycol, water—alcohols and water—urea mixtures of various compositions, and have reported the role of the permittivity of the medium towards such interactions.In previous studies [3,7–9], we have examined the effect of changing the solvent from pure water to 10, 20, 30 and 40 mass % dioxane + water on the dissociation of acids, dissolution of silver salts and standard potentials of the silver—silver chromate electrode. To extend the work, we now report the results of a determination of the standard potentials of the silver—silver thiocyanate electrode and associated thermodynamic parameters for the electrode reaction in these media. However, various thermodynamic quantities for the electrode reaction of this electrode and the dissolution process of silver thiocyanate are known in water [10] and formamide [11].     

A Determination of Standard Potentials and Related Primary pH Standards in the 50 Mass Percent (N-Methyl-2-Pyrrolidinone + Water) Mixture at Various Temperatures

Following the IUPAC-endorsed procedure, the primary pH standards offered by the equimolal phosphate buffer (Na₂HPO₄ (0.01 mol⋅kg⁻¹) + KH₂PO₄ (0.01 mol⋅kg⁻¹)) in the (N-methyl-2-pyrrolidinone + water) solvent mixture of 50 mass percent composition at various temperatures have been determined from potential difference measurements with the reversible Harned cell. Since the essential prerequisite of the above procedure is the knowledge of the (hitherto unknown) standard potential difference of Harned’s cell, a parallel supplementary series of potential difference measurements has been carried out with the reversible cell, Pt|H₂|HCl(m)|AgCl|Ag|Pt according to the classical thermodynamic procedure. The problem of comparability of the pH scale in the (N-methyl-2-pyrrolidinone + water) solvent with that in the pure water solvent is duly discussed in terms of primary medium effects.     

Autoprotolysis constants and standardization of the glass electrode in acetonitrile-water mixtures. Effect of solvent composition

Standard e.m.f.s for the cell GE/HCl/AgCl/Ag/Pt (GE=glass electrode) in acetonitrile-water mixtures containing 0–70% (w/w) of acetonitrile were obtained. Values of the autoprotolysis constant, K_ap, of these mixed solvents were also determined from e.m.f. measurements of the cell GE/KCl + KS/AgCl/Ag/Pt. The influence of variations in the solvent composition on pK_ap values was evaluated. Over the whole of the composition range studied the pK_ap values were linearly correlated with the mole fraction of acetonitrile and with the reciprocal of the relative permittivity of solvent mixtures. Linear relationships were also obtained for pK_ap values vs. the Kamlet-Taft π^★ polarizability/dipolarity parameter in the range 0–50% (w/w).     

Solvent effect on standard electrode potential: Part II. Silver-silver bromide electrode in methanol-water mixtures

The standard potentials of the silver-silver bromide electrode have been determined over a broad range of methanol concentrations from e.m.f. measurements of the cell Pt, H₂(g, 1 atm); HBr(m), X% methanol, Y% water; AgBr, Ag at eight temperatures ranging from 20 to 55°C. The standard e.m.f. has been expressed as a function of temperature. Thermodynamic functions of cell process, the primary medium effect of various media on hydrobromic acid, and thermodynamics of transfer of HBr from water to methanolic media have been computed and discussed in the light of ion-solvent interactions as well as the structural changes of the solvents.     

含CO2/离子液体系统相行为及其在反应与分离中的应用进展

目前已知的绿色溶剂主要包括超临界流体（Supercritical fluids,SCFs）、离子液体（Ionic liquids,ILs）、二氧化碳膨胀液体（CO₂ expanded liquids, CXLs）、水以及上述溶剂的混合物等。其中,由超临界CO₂（Supercritical CO₂,SCCO₂）与ILs混合而构成的新兴溶剂,因为化学热力学方面的特性,成为近年来研究的热点,未来很有发展前景。本文回顾了目前为止在该领域所开展的工作,总结了影响SCCO₂与IL相行为的主要因素。包括温度、压力、ILs的含水量、ILs的阴离子、ILs的阳离子、ILs的摩尔体积以及助溶剂等。同时分析了ILs/SCCO₂与溶质形成的多元混合物相行为的成因。介绍了ILs/CO₂在萃取、反萃取、膜分离、反胶束、萃取与反应耦合等分离方面的应用。由于传统的单元操作很难满足无污染和对过程集成的要求,因而含有ILs/ SCCO₂的分离反应耦合过程将是未来是实现清洁生产的发展方向。     

Hydrogen bonding and the cryoprotective properties of glycerol/water mixtures

Molecular dynamics simulations and infrared spectroscopy were used to determine the hydrogen bond patterns of glycerol and its mixtures with water. The ability of glycerol/water mixtures to inhibit ice crystallization is linked to the concentration of glycerol and the hydrogen bonding patterns formed by these solutions. At low glycerol concentrations, sufficient amounts of bulk-like water exist, and at low temperature, these solutions demonstrate crystallization. As the glycerol concentration is increased, the bulk-like water pool is eventually depleted. Water in the first hydration shell becomes concentrated around the polar groups of glycerol, and the alkyl groups of glycerol self-associate. Glycerol-glycerol hydrogen bonds become the dominant interaction in the first hydration shell, and the percolation nature of the water network is disturbed. At glycerol concentrations beyond this point, glycerol/water mixtures remain glassy at low temperatures and the glycerol-water hydrogen bond favors a more linear arrangement. High glycerol concentration mixtures mimic the strong hydrogen bonding pattern seen in ice, yet crystallization does not occur. Hydrogen bond patterns are discussed in terms of hydrogen bond angle distributions and average hydrogen bond number. Shift in infrared frequency of related stretch and bend modes is also reviewed.     

盐酸在氨基酸水溶液中热力学性质的研究 I. 甘氨酸+盐酸+水体系

Standard potentials (E°_m) of the Ag-AgCl electrode in Glycine+H_2O mixture at 25 ℃, 30 ℃, 35 ℃, 40 ℃, and 45 ℃ have been determined from the EMF measurements of cells of the type: Pt, H (g, 101.325 kPa)|HCl(m)+Glycine+H_2O|AgCl-AgThese values have been utilized to evaluate the transfer energetics (ΔG°_t, ΔH°_t, ΔS°_t) accompanying the transfer of 1 mol HCl from the standard state in water to the standard state in Glycine+H_2O mixtures. Attempts have been made to explain the transfer energetics varying with different compositions of Glycine+H_2O mixtures in the light of ion-solvent interactions and the structureal effects of the solvents.