QUATERNARY DIFFUSION-COEFFICIENTS OF NACL-MGCL2-NA2SO4-H2O SYNTHETIC SEAWATERS BY LEAST-SQUARES ANALYSIS OF TAYLOR DISPERSION PROFILES

Equations are developed to calculate the nine interdiffusion coefficients of four-component solutions by least-squares analysis of the refractive index profiles across Taylor dispersion peaks. The pre-exponential weighting factors and the eigenvalues of the diffusion coefficient matrix are used as the fitting parameters instead of the diffusion coefficients. This simplifies the fitting equations and speeds up the convergence. The analysis is tested on dilute aqueous solutions of sucrose + glycine + urea, and then used to determine the interdiffusion coefficients of aqueous NaCl + MgCl2 + Na2SO4 solutions at compositions corresponding to synthetic seawaters of salinities 5, 15, 25 and 35. The results are used to predict the concentration profiles that develop when seawater interdiffuses with fresh water.