Vapor pressure isotope effects in aqueous systems. VIII. The system dimethyl sulfoxide/H/sub 2/O/D/sub 2/O. [25-70/sup 0/C]

Journal Article · Sun Feb 01 00:00:00 EST 1976 · J. Solution Chem.; (United States)

DOI:https://doi.org/10.1007/BF00648893· OSTI ID:7239064

Chan, T C; Van Hook, W A

Vapor pressures for the system I (dimethyl sulfoxide/H/sub 2/O = DMSO/H/sub 2/O) and isotopic differential pressures I-II (II = DMSO/D/sub 2/O) have been measured between 25 and 70/sup 0/C at DMSO concentrations of 0.05, 0.15, 0.30, 0.45, 0.60, 0.70, 0.80, 0.87, and 0.92 mole fraction. A high-precision differential method was used. The total pressures over the solutions, I, have been fitted to a relation derived from Duhem-Margules equation, P/sup T/ = P/sub 1//sup 0/X/sub 1/..gamma../sub 1/ + P/sub 2//sup 0/X/sub 2/..gamma../sub 2/, with ..gamma../sub 1/ = exp(..sigma../sub k/..cap alpha../sub k/X/sub 2//sup k/ and ..gamma../sup 2/ = exp(..sigma cap alpha../sub k/X/sub 2//sup k/ - ..sigma..(..cap alpha../sub k//(k - 1))(kX/sub 2//sup k-1/ - 1)). The ..cap alpha../sub k/ are parameters and k is a number greater than or equal to 2. The ..cap alpha../sub k/ were taken as temperature dependent. Four parameters sufficed to fit the data within experimental error. Excess partial molal properties derived from the fits are in quantitative agreement with earlier literature results derived from the directly measured partial pressures, but the present data extend over a wider temperature range. The isotopic differential pressures I-II were similarly fitted to the relation above. The excess free energies and enthalpies G/sub I//sup E/ and H/sub I//sup E/ are large and negative. The isotope effects ..delta..G/sub 1/,/sub 11//sup E/ = G/sub 1//sup E/ - G/sub 11//sup E/ and ..delta..H/sub 1/,/sub 11//sup E/ are negative. They are discussed in detail in terms of the theory of isotope effects in condensed phases and demonstrated to be consistent with that theory and with the available spectroscopic data. A small amount of enthalpy data for the solution of DMSO in HOH and DOD is reported.

• Research Organization: Univ. of Tennessee, Knoxville
• OSTI ID: 7239064
• Journal Information: J. Solution Chem.; (United States), Vol. 5:2
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
DEUTERIUM
ISOTOPE EFFECTS
DMSO
VAPOR PRESSURE
HEAVY WATER
WATER
AQUEOUS SOLUTIONS
ENTHALPY
FREE ENERGY
MEDIUM TEMPERATURE
TEMPERATURE DEPENDENCE
DISPERSIONS
ENERGY
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPES
LIGHT NUCLEI
MIXTURES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SOLUTIONS
STABLE ISOTOPES
SULFOXIDES
THERMODYNAMIC PROPERTIES
400202* - Isotope Effects
Isotope Exchange
& Isotope Separation