The fluorophotometric determination of uranium was studied to develop a procedure applicable to the routine analysis of waters. Three grams of the high carbonate flux are used in a dilution procedure with spiking. Because of the comparatively high reflectivity of this large disk and the low uranium concentration, a correction for nonquenched light is required. A formula is developed to compensate for the effect, an electrical fusion device is described, and the problem of fixing uranium in waters is discussed.