X-ray diffraction measurements show that saturation loadings Of C-5-C-13 n-alkanes at room temperature increased the unit cell size of silicalite-1 crystals, and the percent volume expansion correlated linearly with the number of carbon atoms per unit cell. Adsorption of tridecane expanded the zeolite the most (1.53 vol %), but all n-alkanes and alcohols studied expanded MFI crystals. Pervaporation fluxes of isooctane through defects in B-ZSM-5 membranes at 313 K decreased 2 orders of magnitude when n-alkanes were added to the feed, and the percentage decrease correlated with crystal expansion; n-alkanes that expanded crystals more caused the flux through defects to decrease more.