Isotope effects in aqueous systems. 12. Thermodynamics of urea-h4/water and urea-d4/water-d2 solutions

Abstract

Differential vapor pressure measurements yielding osmotoic coefficients and osmotic coefficient isotope effects for urea h/sub 4//H/sub 2/O and urea-d/sub 4//D/sub 2/O solutions (4, 8, 12, 16, 18, 20 m, and saturated) are reported over the temperature range 15 to 60/sup 0/C. Solubilities and apparent molar volumes and their isotope effects (IE's) have also been measured. From these various data as supplemented by information from published sources, we have calculated standard-state (infinite-dilution) and excess partial molar free energies, volumes, enthalpies, and expansivities (and their isotope effects) as appropriate. Raman spectra in the librational and OH and OD stretching regions are reported. The various data are discussed in terms of solution models of the urea/water system in the context of the theory of isotope effects in condensed phases.