Supersonic velocities and adiabatic compressibilities of a series of mixtures of water‐ethyl alcohol‐sodium chloride have been found. In general, maxima of sound velocities and minima of adiabatic compressibilities were obtained. With increase of salt concentration, the depth of the minimum of compressibility decreased and shifted towards the value for alcohol free‐salt water, and for 3Nconcentration of salt, no minimum at all remained. The phenomenon has been explained as caused by the depolymerization of water by sodium chloride. The explanation supports earlier results on the water alcohol system.