We have derived a set of transport equations for heat and mass transfer across a liquid-vapour interface in distillation columns. We have used the entropy production rate on each tray, and integrated through the interface, when the liquid is not in equilibrium with the vapour. The set, that defines overall coefficients of transport, includes contributions from the interface, from the vapour film, and from the liquid film. It is shown, using data for a rectifying column that separates ethanol and water, that the coefficients can be determined by fitting the transport equations to the entropy production rate, with the constant thickness of one of the films as the only adjustable variable. Almost all of the entropy production is due to mass transfer between the phases. Coefficient values were determined for a large and a small value for the film thickness ratio as a function of temperature. The distribution of the entropy production rate between the phases depends largely on the film thickness, but its distribution between mass and heat transfer contribution does not depend on this variable. A contribution from the Soret or Dufour effect is found for large liquid films. The driving force for mass transfer, calculated with coefficients and rates, compared well with average values, which were calculated from the experimental data. The set of equations was compared to the Maxwell-Stefan equation set. Since it contains the interface contribution and coupling, it can be used to asses common approximations.