ANALYTICAL METHOD OF URANIUM (IV) AND URANIUM (VI) IN URANIUM ORES AND URANIUM-BEARING ROCKS

The best conditions for keeping the original valences of uranium during the dissolution and separation procedure of geological samples (expecially those micro u-ranium-bearing rock) were studied. With the exist of high concentration protec-tants, the sample was decomposited with concentration HF at 40 + 5C. The U ( VI ) was dissolved completely and formed stable complex UO2F2, the U ( IV ) was precipitated rapidly and carried by carrier. Quantitative separation was carried out immediately with suction. The decomposition of sample and separation of solid/liquid phases was completed within two minutes. After separation, the U ( IV ) and U ( VI ) were determinted quantitatively with laser fluorescence or volumetry respectively according to the uranium content. The limit of detection for this method is 0.7 ug/g, RSD is 10.5%, the determinate range of uranium is 2 X 10-6 -10-1 g/g. The uranium contents and their valence state ratio were measured for more than one hundred samples of sand stone and granite, the accuracy and precision of these results are satisfactory for uranium geological research.