Karl Fischer reagent comprising iodide, sulphur dioxide with an initial concentration above 0.5 M, and imidazole/imidazole derivative dissolved in alcoholic solvent, whereby the molar ratio between the initial imidazole/imidazole derivative concentration and the initial sulphur dioxide concentration is above 10. The reagent contains a modifying substance that is an aliphatic hydrocarbon, or a primary or secondary alcohol, or a combination thereof. A method for the determination of water content by means of Karl Fischer coulometric titration in a diaphragm-free cell, whereby the Karl Fischer reagent is used, and the coulometric titration is carried out in a diaphragm-free cell. Use of the Karl Fischer reagent in a method for the determination of water content by means of coulometric titration.