E. Yu. Lebedeva

Volumetric properties of H2O, D2O, and methanol in acetonitrile at 278.15—318.15 K

The densities of H2O, D2O, and MeOH solutions in acetonitrile with the solute concentrations up to 0.07 molar fractions at 278.15, 288.15, 298.15, 308.15, and 318.15 K were measured using vibrating-tube densimetry with an error ≤8·10–6 g cm–3. The limiting partial molar volumes for the H/D isotopomers of water and IaII in acetonitrile (V–2∞) and the isotope effects in V–2∞ and in excess molar volumes of acetonitrile—water mixtures were calculated. Molecules of H2O, D2O, and IaII form associates with acetonitrile molecules via hydrogen bonds. The associates have the packing volumes close to those in the individual solute. The water and methanol molecules were assumed to be incorporated into the acetonitrile structure without substantial changes in the latter. However, this process results in some compression of the system with a simultaneous increase in its expansibility.

Influence of Water Microimpurities on Acetone Structure: Volume Effects of H 2 O and D 2 O Solvation

Here, we report the limiting partial molar volumes of ordinary water (H 2 O) and heavy water (D 2 O) in acetone and the excess molar volumes of these mixtures derived from precision density measurements at T = 288.15‐318.15 K and p ≈ 0.1 MPa. We have found the following. In the presence of water microimpurities (with water mole fractions up to 0.03), the molecular packing of acetone acquires a greater expansibility due to the appearance of new structural fragments (solvate complexes) in which bonding is stronger than in the bulk of the solvent. This weakens acetone‐acetone interactions and loosens the initial solvent structure as a whole; the effect is especially noticeable for the limiting dilution of acetone solutions of heavy water. We discovered the nontrivial fact that the negative (in sign) isotope effect on the limiting partial molar volume of water dissolved in acetone increases considerably with rising temperature. Acetone of high purity grade (from Khimmed; no more than 0.008 wt % water according to Fisher’s test) was used in experiments. Bidistilled water of the natural isotope abundance (electrical conductivity σ ≈ 1.3 × 10 –5 S/m) and heavy water D 2 O (from Izotop; 99.92 ± 0.02 wt % D) (based on density [3]) were used to prepare solutions. The solutions were prepared by a gravimetric method by diluting the degassed host solvent accurate to 2 × 10 ‐5 c sm,2 units, where c sm,2 is the solvomolality of the water isotopologue. Solvomolality c sm,2 is a dimensionless parameter of the solution compositions expressed through

Solubility and thermodynamics of dissolution of helium in water at gas partial pressures of 0.1–100 MPa within a temperature range of 278–353 K

The tables of recommended numerical values for the water solubility of helium at gas partial pressures of 0.1–100 MPa within a temperature range of 278.15–353.15 K are given. The thermodynamic characteristics of dissolution of helium in water at the mentioned parameters of state have been calculated. The independence of the dissolution enthalpy on the pressure has been recognized and explained.

Effects of electrolyte concentration, temperature, and pressure on the sechenov salt-effect parameter: He-NaCl-H2O system

The data on the solubility of helium in water and aqueous solutions of sodium chloride at a temperature of T = 293–353 K and a He partial pressure of p2 = 0.1–20 MPa are used to calculate the standard parameters of the Sechenov salt effect and estimate, within the formalism of the McMillan-Mayer theory, the parameters of the pairwise solute-solute interaction.

Solubility and Thermodynamics of Solvation of Krypton in Mixtures of H/D Isotopomers of Water and Methanol at 101325 Pa and 278-318 K

The solubility of krypton in mixtures of H/D isotopomers of water (H2O, D2O) and methanol (CH3OH, CD3OH, CH3OD) was studied at 101325 Pa and 278.15-318.15 K with a 10 K step. The thermodynamic characteristics of Kr solvation were calculated. The densities of mixtures of water and methanol isotopomers at the examined temperatures were calculated with an error of no more than 1 × 10-5 g cm-3 in the entire composition range. Both in water and aqueous methanol, krypton behaves as a structure-making component, but the alcohol solvation surrounding of the Kr atoms is more labile and more susceptible to the breaking effect of temperature.

Pitzer equation for the enthalpy of solution of electrolytes in N,N-dimethylformamide in a wide temperature range

Binary interaction parameters of the Pitzer equation are calculated from available enthalpies of solution of KI, NH4Br, (C2H5)4NBr, and (n-C4H9)4NI inN,N-dimethylformamide (DMF) at 233-323 K. The Pitzer parameter βMX(1)L, which characterizes the short-range interaction between unlike charged ions, is negative, and its absolute value increases with decreasing temperature. Between 313 and 323 K, the binary ion-ion interactions in DMF are essentially independent of temperature.

Chiral effect in the sechenov parameters of argon solubility in aqueous α-valine and α-phenylalanine solutions

Data on the solubility of argon in water and aqueous solutions of L and D enantiomers of α-valine and α-phenylalanine at T = 283–328 K and partial pressure of argon p2 = 0.1 MPa are used to calculate the standard parameters of the Sechenov salt effect. Parameters of the solute-solute pair interaction are estimated within the formalism of the McMillan-Mayer theory. Evidence is provided for the presence of the chiral effect in the Sechenov parameters.

Solubility and thermodynamics of solvation of krypton in aqueous-methanol solutions of urea at 101 325 Pa and 278–318 K: I. Effect of H/D isotope substitution

The solubility of Kr in H2O-CD3OH-CO(NH2)2 and D2O-CH3OD-CO(ND2)2 mixtures in the entire range of compositions of the mixed aqueous-methanol solvent at a urea content of up to 1.5 solvomolality units (mole fraction 0.0263) was measured at 101 325 Pa and 278.15–318.15 K (at 10 K step). The standard Sechenov parameters KS0 of the solubility of Kr and the thermodynamic parameters of krypton-urea pair interactions were determined. A differentiating effect of the H/D isotope substitution on KS0 was revealed: Upon deuteration of groups participating in strong hydrogen bonding, the Sechenov solubility parameter increases, and upon replacement of CH3 by CD3, decreases in the absolute value.

Effect of H/D-isotope substitution on the solubility and solvation thermodynamics of krypton in methanol solutions of carbamide

The solubility of gaseous krypton in CO(NH2)2—CH3OH (CD3OH) and CO(ND2)2—CH3OD solutions with carbamide concentrations of up to 1.5 solvomolality units (∼0.026 mole fractions) was measured at 278, 288, 298, 308, and 318 K and at a partial gas pressure of 101325 Pa. The thermodynamic functions of dissolution (solvation) of krypton and the standard Setchenov coefficients were calculated. The solvation of Kr molecules increases upon deuterium substitution and with an increase in the temperature and carbamide concentration. In these solutions, specific contacts between the carbamide and methanol molecules play the predominant role.