Isothermal diffusion coefficients for sodium chloride-magnesium chloride-water at 25.degree.C. 4. Solute concentration ratio of 1:3

Isothermal interdiffusion coefficients have been obtained by Guoy interferometry for the ternary system NaCl-MgCl{sub 2}H{sub 2}O at 25.00{degree}C and a 1:3 molarity ratio of NaCl to MgCl{sub 2}. Data are reported for total molar concentrations of 0.5, 1.0, 2.0, 3.0, and 3.6 M. The main-term diffusion coefficient D{sub 22}, for the flow of MgCl{sub 2} due to its own gradient, changes by only 13% over the above concentration range. In contrast, D{sub 11} for the flow of NaCl due to its own gradient is higher than D{sub 22} at low concentration, and decreases sharply to less than 1/2 its initial value at 3.6 M. Moreover, it crosses the value of D{sub 22} at about 1.2 M. Densities were measured for all solutions.