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A simple dual impedance tester has been designed for determining the water content in organic solvents. The detection cells are formed by a pair of semi-cylindrical electrodes of aluminium foil, located opposite one another around the outer surface of a glass tube with the tested solution. Thus, the electrodes are not in contact with the analysed solution. The detection cells are connected as a capacity determining the frequency of the integrated multivibrator. The analytical signal is the difference between the frequency of the multivibrator with the measuring cell filled with the analysed solution and the multivibrator with the cell filled with pure anhydrous solvent. Solvents with various permittivities and water contents to 50% v/v were tested, with a detection limit from 0.2% (dioxane) to 1.4% (acetonitrile). The method can also be used for determining the relative permittivity of solvents with various water contents. The detector can even be used outside the laboratory because it can be powered by a standard 9-V battery. [ABSTRACT FROM AUTHOR]