The acidity of A1-, Cr(III)- and Fe(III)- exchanged montmorillonite was characterised utilising the bases pyridine and n-butylamine which occupy three different sites in the interlamellar space: (i) physisorbed base (ii) base bound to Lewis sites and (iii) protonated base. The Al- and Cr(III)-forms were found to be very temperature stable whereas the Fe(III)- form was not. Isothermal gravimetry in the temperature range 18 - 105 °G was used to measure the rate of sorption of three alcohols, methanol (MeOH), propan-2-ol (i-PrOH), and 2-methylpropan-2-ol (t-BuOH), and three cyclic ethers, 1,4-dioxan (DIOX), tetrahydropyran (THP) and tetrahydrofuran (THF), from the vapour phase, onto the three cation exchanged forms. The rate of alcohol uptake increased as t-BuOH< i-PrOH< MeOH with integral diffusion coefficients, D, ranging from -17 2 -1 3.0-16.0 x 10 m s . The sorption rate for i-PrOH and t-BuOH following the sequence Fe ( III) <. Cr ( III) ^ Al whereas the cyclic ethers follow the sequence Cr(III)^Fe(III)-c A l . Activation energies for all the solvents lie between 2.0 kJ mol ^ and 13.0 kJ mol In the adsorption of cyclic ethers from binary liquid mixtures with methanol the isotherm type is dominated by the binary mixture whereas the amplitude, which follows the sequence DI OX «£ THP THF is further influenced by the exchanged cation. Altering the level of hydration shifts the azeotropic point in favour of the cyclic ethers DI0X and THP, but only affected the amplitude of the THF/MeOH system.