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Journal of Structural Chemistry

2010 year, number 1

THERMAL COEFFICIENTS AND INTERNAL PRESSURE OF AQUEOUS UREA. CONCENTRATION, TEMPERATURE, AND ISOTOPY EFFECTS

V. P. Korolev
Keywords: urea, aqueous solutions, thermal coefficients, internal pressure
Pages: 81-87

Abstract

The thermal expansion α, isothermal compressibility βT, and internal pressure coefficients of Н2О-(NH2)2CO and D2O-(ND2)2CO π systems at 278 K, 298 K, and 318 K and aquamolality m ≤ 1.5 were calculated. The changes in the isotope differences Δα, ΔβT, and Δπ at different solute concentrations and temperature are discussed. In contrast to Δα and Δπ, ΔβT is almost independent of the urea concentration already at 298 K and independent of m at 318 K. The derivative ∂π/∂Т increased in dilute solution, at lower temperatures, and on passing from protium to deuterium system, which corresponded to increased structuring. The isotope difference for the Grüneisen constant at given temperatures and concentrations is shown to be independent of the urea content.