Densities and Volumetric Properties of Aqueous Solutions of {Water (1) + <i>N</i>‑Methylurea (2)} Mixtures at Temperatures of 274.15–333.15 K and at Pressures up to 100 MPa

Densities of the mixture {water (1) + <i>N</i>- methylurea (2)} in the concentration range to mole fraction <i>x</i>₂ = 0.07071 (or to the solution molality concentration <i>m</i>₂ = 4.22335 mol·kg^–1) at atmospheric pressure in the temperature range from 274.15 to 333.15 K and compression <i>k</i> = Δ<i>V</i>/<i>V</i>₀ at pressures to 100 MPa (10, 25, 50, 75, and 100) in the temperature range from 278.15 to 323.15 K (278.15, 288.15, 288.15, 308.15, 323.15) in the same concentration range were calculated in this study. The apparent molar volumes of <i>N</i>-methylurea <i>V</i>_ϕ,2 and the partial molar volumes of both components <i>V̅</i>₁ and <i>V̅</i>₂ in the mixture, molar isothermal compressibilities <i>K</i>_<i>T,m</i>, molar isobaric thermal expansions <i>E</i>_<i>P,m</i>, and isochoric coefficients of thermal pressure β of the mixture were calculated. Moreover, volumetric measures for the infinitely dilute solution of <i>N</i>-methylurea solution were calculated: limiting partial molar volumes <i>V̅</i>₂^∞, the limiting partial molar isothermal compressibilities <i>K̅</i>_<i>T</i>,2^∞, and the limiting partial molar isobaric thermal expansions <i>E̅</i>_<i>P</i>,2^∞. The results obtained are discussed from the point of view of solute–solvent and solute–solute interactions

Densities and Molar Isobaric Thermal Expansions of the Water + Formamide Mixture over the Temperature Range from 274.15 to 333.15 K at Atmospheric Pressure

The density of the {water (1) + formamide (2)} mixture has been measured over the whole composition range at temperatures from 274.15 to 333.15 K at atmospheric pressure using the vibration densimeter. The volumetric parameters of the mixture, such as the excess molar volume, molar isobaric thermal expansions, and apparent and partial molar volumes of water and formamide, as well as their limiting values, have been calculated. It was shown that the mixture formation resulted in the volume decrease at all temperatures, and the largest absolute value of the excess molar volume corresponded to the mixture composition of 2H₂O-FA. The limiting partial molar volumes of water and formamide increased with the temperature rise. At a temperature of about 323 K the limiting partial molar volume of water became larger than its own molar volume

Density and Volumetric Properties of Aqueous Solutions of Trimethylamine <i>N</i>‑Oxide in the Temperature Range from (278.15 to 323.15) K and at Pressures up to 100 MPa

Densities of aqueous solutions of trimethylamine <i>N</i>-oxide (TMAO) were measured over the concentration range (0.0875 to 4.3251) mol·kg^–1 at temperatures (278.15, 288.15, 298.15, 308.15, and 323.15) K and pressures (0.101, 10, 25, 50, 75, and 100) MPa. Volumetric properties such as apparent molar volume of TMAO, <i>V</i>_ϕ,2, molar isothermal compression, <i>K</i>_<i>T</i>,m, molar isobaric expansion, <i>E</i>_<i>P</i>,m, and internal pressure, <i>P</i>_int, of its aqueous solutions were calculated depending on concentration, temperature, and pressure. The volumetric partial properties of TMAO at infinite dilution in water (<i>V</i>₂^∞, <i>K</i>_<i>T</i>,2^∞, and <i>E</i>_<i>P</i>,2^∞) were also determined. The results were discussed from the standpoint of solute–solute and solute–solvent interactions