surface plane d'eau

CONT: It was established by Lord Kelvin that the vapour pressure over the surface of a water drop in equilibrium with its surroundings is greater that over a plane water surface. This vapour pressure difference is inversely proportional to the radius of the drop. The vapour pressure over a drop is then greater than the saturation vapour pressure for the liquid concerned, since the saturation vapour pressure is defined as that over a plane surface.