Binary mutual diffusion coefficients of aqueous alcohols. Methanol to 1-heptanol

Mutual diffusion coefficients, measured by Taylor dispersion at 25 degrees C, are reported for binary aqueous solutions of methanol, ethanol, isomeric propanols and butanols, 1-pentanol, 1-hexanol, and 1-heptanol. Limiting diffusion coefficients (D-0) for the l-alkanols are found to decrease with alcohol molar volume V approximately as V--1/2. Although values of D-0 for aqueous 1-propanol and 2-propanol are nearly identical within experimental error, the limiting diffusion coefficients of the isomeric butanols differ by up to 10% and increase in the order D-0(2-methyl-2-propanol) < D-0(2-butanol) approximate to D-0(2-methyl-1-propanol)) < D-0(1-butanol). The butanol results illustrate the difficulty of predicting accurate diffusion coefficients for aqueous solutions.