 
Summary: Mutual Diffusion Coefficients and Densities at 298.15 K of Aqueous
Mixtures of NaCl and Na2SO4 for Six Different Solute Fractions at a
Total Molarity of 1.500 mol,dm3 and of Aqueous Na2SO4
Onofrio Annunziata,
Joseh A. Rard,*,
John G. Albright,
Luigi Paduano,§
and Donald G. Miller
Chemistry Department, Texas Christian University, Fort Worth, Texas 76129, and Geosciences and
Environmental Technologies, Earth and Environmental Sciences Directorate, Lawrence Livermore National
Laboratory, University of California, Livermore, California 94550
Isothermal mutual diffusion coefficients (interdiffusion coefficients) were measured for ternary aqueous
mixtures of NaCl and Na2SO4 at a constant total molarity of 1.500 mol,dm3 at 298.15 K, using Rayleigh
interferometry with computerized data acquisition. The experiments were performed at NaCl molarity
fractions of z1 ) 1, 0.90, 0.75, 0.50, 0.25, and 0. These measurements supplement our earlier results at
total molarities of 0.500 and 1.000 mol,dm3. Diffusion coefficients were also measured at three additional
concentrations of Na2SO4(aq). Densities of all solutions were measured with a vibrating tube densimeter.
At all ternary solution compositions, one crossterm diffusion coefficient has small negative values whereas
the other has larger positive values. Comparing the results at 0.500, 1.000, and 1.500 mol,dm3 shows
that both mainterm diffusion coefficients decrease with increasing total concentration at any fixed value
