In the routine fluorimetrie procedure of the U, S* Geological Survey for the determination of uranium in the ash of plants, over 99 percent of the determinations during the past %year fall in the range Q.^ to 50 ppm* The method uses a simple nitric acid leach for solution of the ashed sample, Elements that wuld interfere are eliminated by extracting uranium present with ethyl acetate after addition of aluminum nitrate as a salting agent. The extracted uranium is fused with a fluoride-carbonate

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... lux, and the intensity of fluorescence produced in the cooled melt by ultraviolet light is measured in a transmission fluorimeter. The precision of results in the range from 0.^ to 35 ppa uranium in plant ash is expressed by a simple equation (standard deviation = 0*063 U 0*15, where U is the observed uranium concentration in parts per million)* This equation is based on 319 pairs of determinations, made during a period of about a year, on samples consisting of ash from sage brush, pinon pine, ponderosa pine, and juniper*