Abstract
This Note presents a new method to measure the equilibrium vapour pressure of water in a complex medium. In this article a "complex medium" refers to a medium in which physico-chemical interactions alter the thermodynamical properties of the water, especially its activity and its equilibrium vapour pressure. This new method consists in placing a sample of the complex medium in a temperature-controlled chamber which volume can be incrementally increased by means of a piston. The equilibrium vapour pressure can be deduced from the variation of the equilibrium total pressure measured for each volume increment. The method has been validated on various saturated salt solutions and on a reference soil.