The Measurement of Heat Capacity Differences Due to the Change of Water Structure in Aqueous Solutions of Organic Compounds

In order to observe more directly the structural organization of water molecules around a non-polar molecule in an aqueous solution, heat capacity differences between two kinds of solutions (solution I and II) of quaternary ammonium salts were measured. In the solution I stable water structure was retained as much as possible and in the solution II water structure was destroyed either by heating to high temperatures or by irradiating with ultrasonic waves. It was found that the heat capacity differences ((Cp)II-(Cp)I) were slightly positive and its maximum values corresponded to 7-8 percent of the heat capacity of pure water itself.