Conductance of Selected Alkali Metal Salts in Aqueous Binary Mixtures of 2-Methoxyethanol at 25°C

Precise conductance measurements have been performed for lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, sodium perchlorate, and sodium tetraphenylborate in 2-methoxyethanol–water mixtures at four different mole fractions, i.e., 0.056, 0.136, 0.262, and 0.486 of 2-methoxyethanol (69.73 D 26.55) at 25°C in the concentration range 0.0004–0.0642 mol-dm^–3. The limiting molar conductivity °, the association constant K _A, and the association distance R for the solvent mixtures have been evaluated from the conductance concentration data using the 1978 Fuoss conductance equation. The single-ion conductances have been estimated using the reference electrolyte tetrabutylam-monium tetraphynylborate(Bu₄NBPh₄). The analysis of the data indicates that for most salts ion association is appreciable in the solvent mixtures with a mole fraction of the cosolvent of 0.262 or higher. The results have been interpreted in terms of ion-solvent interactions and structural changes in the mixed solvent media.     

The Solubility of Hydrogen Sulfide in Acetonitrile at 25°C

Abstract

The solubility of hydrogen sulfide in acetonitrile at 25°C has been determined both gravimetrically and titrimetrically to be 0. 528 M. The effects of the presence of water and an electrolyte (LiClO₄) on this parameter are reported.     

Volumetric Properties of Binary Mixtures of Acetonitrile and Chloroalkanes at 25°C and Atmospheric Pressure

Excess molar volumes for binary mixtures of acetonitrile + dichloromethane, acetonitrile + trichloromethane, and acetonitrile + tetracloromethane at 25°C have been used to calculate partial molar volumes , excess partial molar volumes , and apparent molar volumes of each component as a function of composition. The V _m ^Evalues are negative over the entire composition range for the systems studied. The applicability of the Prigogine–Flory–Patterson theory was explored. The agreement between theoretical and experimental results is satisfactory for the systems with dichloromethane and tetrachloromethane. For the unsymmetrical behavior of the system with trichloromethane, however, the agreement is poor.     

Thermodynamics of NaCl in Aqueous Ethylene Glycol, Acetonitrile, and 1,4-Dioxane Mixtures from Emf Measurements at 25°C

The electromotive force of the amalgam cell {Na_xHg_1-xNaCl(m)AgClAg} has been measured at 25°C as a function of the mole fraction x of Na in amalgams and of the molality m of NaCl in (ethylene glycol + water), (acetonitrile + water), and (1,4-dioxane + water) mixed solvents, containing up to 0.8 mass fraction of the organic component, with relative permittivities 27. The relevant standard molal electromotive forces have been determined, together with the mean molal activity coefficient _± of NaCl as a function of its molality. In the case of (ethylene glycol + water) mixtures, a linear dependence of on the mass fraction of ethylene glycol is observed, which is quite unusual, The Debye-Hückel equation is applicable successfully over the whole range of molalities explored, which extends to the vicinity of the solubility limit of NaCl in each solvent. The dependence of the standard emf on the logarithm of the volume fraction of water in the aqueous-organic solvent mixtures have been analyzed in terms of Feakins and French's theory, leading to a primary hydration number 7.2 for NaCl, in good agreement with previous results employing different methods.     

Dissociation Constants for Citric Acid in NaCl and KCl Solutions and their Mixtures at 25 °C

The constants for the dissociation of citric acid (H₃C) have been determined from potentiometric titrations in aqueous NaCl and KCl solutions and their mixtures as a function of ionic strength (0.05–4.5 mol-dm^–3) at 25 °C. The stoichiometric dissociation constants (K_i^*)

Activity coefficients for NaBr in ethanol-water mixtures at 25°C

Activity coefficients for NaBr in ethanol-water mixtures with 0, 20, 40, 60, 70, 80, 90 and 99.9 weight% of ethanol have been determined at 25°C from the emf measurements of the galvanic cells

Electrical Conductance of Some Symmetrical Tetraalkylammonium and Alkali Salts in N,N-Dimethylacetamide at 25°C

Precise measurements of electrical conductances of solutions of tetraethylammonium bromide, tetrapropylammonium bromide, tetrapentylammonium bromide, tetrahexylammonium bromide, tetraheptylammonium bromide, tetraocytylammonium bromide, sodium tetraphenylborate, and potassium tetraphenylborate in N,N-dimethylacetamide at 25^°C are reported for the concentration range 0.005-0.015 mol-dm^–3. The conductance data have been analyzed by the 1978 Fuoss conductance-concentration equation in terms of the limiting molar conductance, the association constant, and the association diameter. The limiting ionic conductances have been estimated from the appropriate division of the limiting molar conductivity value of the reference electrolyte Bu₄NBPh₄. Slight ionic association was found for all these salts in this solvent medium. Tetraalkylammonium ions are found to be unsolvated in N,N-dimethylacetamide, whereas significant solvation has been noticed for sodium and potassium ions.     

Isopiestic Determination of Osmotic and Activity Coefficients for Solutions of LiCl, LiBr, and LiNO3 in 2-Propanol at 25°C

The osmotic coefficients of lithium chloride, lithium bromide, and lithium nitrate in 2-propanol have been measured by the isopiestic method at 25^°C. Sodium iodide was used as the isopiestic standard. The molality ranges covered were from 0.2 to 1.5 for LiCl and LiBr, and to 1.9 mol-kg^-1 for LiNO₃. The system of equations developed by Clegg–Pitzer and Pitzer were used to fit each set of osmotic coefficients. The experimental osmotic coefficient data are successfully correlated with these models. The parameters from the fit were used to calculate the mean molal activity coefficients.     

Complexation Properties of a Carbon-Bridged Cryptand with Metal Ions in Aqueous Solution at 25°C

Abstract

Thermodynamic quantities (log K, ΔH, and ΔS) for the interactions of a carbon-bridged cryptand with Li⁺, Na⁺, K⁺, Ca²⁺, Sr²⁺, Ba²⁺, and Pb²⁺ were determined at 25° C by calorimetric titration in aqueous solution. The cryptand forms complexes with Na⁺, Sr²⁺, Ba²⁺, and Pb²⁺ with log K ≤ 2. Complexation was not detected for Li⁺, K⁺, and Ca²⁺. Weak interactions with Li⁺ and K⁺ and a log K value of 2.4 for Na⁺ suggest that the cavity size of the cryptand is close to that of Na⁺ but too small for K⁺ and too large for Li⁺. The carbon-bridged cryptand selectively binds Sr²⁺ (log K = 3.2) over Ca²⁺ and Ba²⁺ by more than one order of magnitude.     

Excess Molar Volumes of Binary Mixtures of Hexanol and Polyethers at 25°C

Excess molar volumes V_m^E at 25°C and atmospheric pressure over the entire composition range for binary mixtures of 1-hexanol with n-polyethers: 2,5-dioxahexane, 3,6-dioxaoctane, 2,5,8-trioxanonane, 3,6,9-trioxaundecane, 5,8,11-trioxapentadecane, 2,5,8,11-tetraoxadodecane, and 2,5,8,11,14-pentaoxapentadecane are reported from densities measured with a vibrating-tube densimeter. Systems containing 2,5-dioxahexane, 2,5,8-trioxanonane, 2,5,8,11-tetraoxadodecane or 2,5,8,11,14-pentaoxapentadecane are characterized by V_m^E > 0, probably due to predominant positive contributions to V_m^E from the disruption of H bonds of 1-hexanol and to physical interactions. In contrast, mixtures with 3,6-dioxaoctane, 3,6,9-trioxaundecane, and 5,8,11-trioxapentadecane are characterized by V_m^E < 0, indicating that the negative contribution to V_m^E from interstitial accommodation is more important.     

Selective Anodic Dissolution of Ag–Zn Alloys in the Eutectic Melt of Alkali Metal Chlorides at 300°С

Russian Journal of Electrochemistry - The peculiarities of electrochemical dealloying of two homogeneous Ag–Zn alloys in the (LiCl)0.57(CsCl)0.26(KCl)0.17 melt are studied. The zinc content...     

Volumetric Properties of Acetonitrile with 1,2-Alkanediols (C2–C6) at 20°C

Dilatometric measurements of excess molar volumes, V^E and excess partial molar volumes, [`(V)] <sub>\texti</sub><sup>\textE</sup>\overline V _{\text{i}}^{\text{E}} have been made for binary mixtures of acetonitrile with 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol at 20°C over the entire composition range. V<sup>E</sup> for acetonitrile + 1,2-ethanediol and 1,2-propanediol mixtures are negative over the entire range of mole fractions and positive values are obtained for all remaining mixtures. The results are explained in terms of dissociation of the self-associated 1,2-alkanediol molecules and the formation of aggregates between unlike molecules through O—H...N=C hydrogen bonding. From the experimental results, V<sup>E</sup> were calculated and correlated by Redlich–Kister type function in terms of mole fractions. The excess partial molar volumes were extrapolated to zero concentration to obtain the limiting values at infinite dilution, [`(V)] _\texti^\textE,o\overline V _{\text{i}}^{{\text{E,o}}} .     

Viscosity of Hg5Tl2 at 14.5°C

Abstract

By means of a toroidal oscillating viscometer, the shear viscosity of some mercury-thallium alloys has been measured in the composition range 28.5–29.5 atomic percent thallium and over the temperature range from 12.5–15.5°C. Some discussion of the experimental results is given in terms of liquid coordination number.     

Solubility in the LaCl3-YbCl3-HCl-H2O System at 25°C

Solubility has been studied in the LaCl₃-YbCl₃-HCl-H₂O water-salt system at 25°C along the (40 ± 0.2)% HCl section; this is a eutonic-type system. The composition of the eutonic solution is as follows (wt %): LaCl₃ · 7H₂O, 4.67, YbCl₃ · 6H₂O, 0.37; HCl, 37.98; and H₂O, 56.98.     

Enthalpies of Dilution of Some Aqueous Transition Metal Sulfate Solutions at 25°C

Enthalpies of dilution of aqueous solutions of the transition metal sulfates CoSO₄, MnSO₄, and NiSO₄, were measured from 1.5 to 0.2 mol-kg^–1 at 25°C. The apparent molal enthalpy equations of Pitzer were fit to the resulting data and the parameters for these equations presented.     

Aluminum electrode for electrochemical studies in cryolite-alumina melts at 700–960°C

The paper presents the results of tests of different aluminum electrode designs for electrochemical studies in cryolite-alumina melts in the temperature range of 700?C960°C. Their operation as regards stability and reproducibility of the potential and the highest activity of metallic aluminum is analyzed. The new design of the aluminum electrode is suggested that is characterized by a more stable and reproducible potential, as compared to the designs earlier suggested. Herewith, the activity of metallic aluminum is higher. It is shown that the suggested electrode is suitable for operation in cryolite-alumina melts in the temperature range from 700°C. The electrode can be used for a prolonged time. Herewith, its potential remains stable and reproducible.     

Carbon electrode for electrochemical studies in cryolite-alumina melts at 700–960°C

The paper presents the results of tests of different carbon electrode designs for electrochemical studies in cryolite-alumina melts in the temperature range of 700?C960°C. Operation of the electrode and its applicability as the reference electrode is analyzed. The theoretical value of the maximum possible instability of its potential related to instability of the gas composition is calculated. A new design of the carbon electrode is suggested in which the gas composition is much more stable. It is shown that the suggested electrode is suitable for application as the reference electrode in cryolite-alumina melts in the temperature range of 750°C and above. The electrode can be used for a prolonged time. Herewith, its potential remains stable and reproducible.     

Enthalpies of Dilution of Cobalt–Amine-Type Salts in Aqueous Solutions at 25°C

The enthalpies of dilution for aqueous solutions of [Co(en)₃]Br₃, [Co(pn)₃]Cl₃, and [Co(tn)₃]Cl₃ (where en = 1,2-diaminoethane, pn = 1,2-diaminopropane, and tn = 1,3-diaminopropane) have been measured at 25°C, and up to m = 1 mol-kg^–1, using an isoperibol calorimeter by the long-jump method. Relative apparent molar enthalpies L have been extracted as an empirical equation relating L and m. Previously reported experimental data and theoretical predictions in the restricted primitive model (RPM) for 3:1 and 1:3 aqueous electrolytes are shown together with the new experimental material.     

Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monomethyl Ether–n-Alcohol Mixtures at 25°C

The excess molar volumes V ^E have been measured for binary mixtures of triethylene glycol monomethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol as a function of composition using a continuous–dilution dilatometer at 25°C at atmosphere pressure. V ^E are negative over the entire range of composition for the systems triethylene glycol monomethyl ether + methanol, + ethanol, and + 1-propanol, and positive for the remaining systems, containing 1-pentanol and + 1-hexanol. V ^E increases in a positive direction with increasing carbon chain length of the n-alcohol. The excess partial molar volumes V _i ^E of the components were evaluated from the V ^E results. The behavior of V ^E and V _i ^E with composition and the number of carbon atoms in the alcohol molecule is discussed.     

Interaction in the manganese sulfate-carbamide-sulfuric acid-water system at 25°C

Heterogeneous equilibria in the manganese-carbamide-sulfuric acid-water quaternary system at 25°C are studied using the solubility method. The concentration boundaries are determined for crystallization of the initial solid components, eutectic compositions of the ternary systems, and binary compounds formed in the carbamide-sulfuric acid-water and carbamide-manganese sulfate-water systems, as well as for new compounds simultaneously containing carbamide, manganese sulfate, and sulfuric acid at a 1: 4: 1 and 1: 2: 1 ratios.