The densities of mixtures of the six possible combinatons of the major sea salts (NaCl, Na2SO4, MgSO4, and MgCl2) were determined at constant ionic strengths of I=1.0 and I=3.0 at 25°C. The results are used to determine the volume changes for mixing (ΔVm) the major sea salts. The values of ΔVm were fit to equations of the form ΔVm where yi is the molal ionic strength fraction of solute i, and υ0 and υ1 are parameters related to the interaction of like-charged ions. The cross-square rule was found to hold at both ionic strengths. Density estimates were made without and with the addition of volume of mixing terms to Young's Rule and compared to the experimental values. The densities calculated with the addition of volume of mixing terms gave better estimates, demonstrating that the densities of concentrated brines can be more accurately estimated using ΔVm terms. The equations of Reilly and Wood which include the cross-square rule were used to estimate the densities of the cross mixtures (NaCl-MgSO4 and MgCl2-Na2SO4). The estimated densities agree with the measured values to within ±30 ppm at I=1.0 and ±125 ppm at I=3.0.
- Sea salts
- volumes of mixing
ASJC Scopus subject areas
- Molecular Biology
- Physical and Theoretical Chemistry