The non-linearity of plots of Delta P versus Delta T in measurements of the Onsager heat of transport at a gas-liquid interface was previously attributed to a difference in thermal accommodation coefficients between dry and wetted states of the solid surface at which AT was applied. This implies that the accommodation coefficient should be a measure of the fractional coverage of the upper surface, as described by Brunauer-Emmett-Teller (BET) theory. A BET treatment of our accumulated AP versus AT data has given values for the average number of layers of adsorbed liquid in the wetted area for aniline, n-heptanol, water, and p-tert-butyltoluene. (c) 2007 Elsevier B.V. All rights reserved.