The author has quantitatively determined the thorium contents of some pitchblends from representative uranium ore deposits in France. The chemical analysis has been effectuated by the “anion exchange-T. T. A. extraction-spectrophotometry by thoron” method. The loss of thorium which happened to occur during the operations has been evaluated using UX1 as radio-isotopic tracer.
The thorium contents ranged from several ppm to the order of 10ppm, and such values which are not so higher than those in granitic rocks show the immobility of thorium in the process of epi-hydrothermal mineralization of uranium in the granitic rocks.
