In this article we develop various experimental methods for measuring the suction and the chemical potential of water and ethanol in soil. The results obtained are in good agreement between the method using the filter paper and the sorption isotherm at low water contents. The precision is less good for the high water contents between the filter paper for water and the box of Richards for ethanol. To analyze the behavior of an ethanol solution in hygroscopic domain, we have used the chemical potential of each component and we showed that this thermodynamic quantity is highly sensitive to the presence of another component and to the surface layers. So, a new device called fragmentation activimeter has been used to measure all the parameters necessary to determine the chemical potential. The results obtained for all the methods are in good agreement with physical behavior of an aqueous solution of ethanol in hygroscopic soil.