A new technique for the determination of water in minerals is described. As in theBrush andPenfield technique, the water is evolved by ignition, condensed, and collected. This step is conducted in aPregl micromuffle bearing a special collecting tube. The final step in the determination of the water, however, is volumetric, rather than gravimetric. For this purpose, theKarl Fischer reagent, dispensed from a microburette, is used. The titration is conducted in a cell designed for external magnetic stirring and with provision for the electrometric determination of the end point. The method is quite rapid. In general, one operator could conduct both the ignition and titration steps faster than a second operator could weigh out the next sample. The precision of duplicate determinations is of the order of 0,5%, and the accuracy of the method is usually better than 1%.