Catalytic determination of traces of uranium in rocks by chronocoulometry

The chronocoulometric method for the determination of trace levels of uranium based on the catalytic reduction of nitrate described in a preceding article, was applied and evaluated with real and synthetic samples Samples with complex matrixes like rocks were first solubilized in h9ot acid (HF+ HNO 3 ) by digestion under pressure in a PTFE bomb. When necessary, liquid‐liquid exraction with tri‐ n ‐ butyl phosphate (TBP) followed by reversion to aqueous phase was used for previous separation of interferents. Results for a feldspar, a phosphorite, and three granitic rock in the range of 2 to 100 ppm, are in good agreement with those obtained by other tedhniques such as X‐ray fluorescence, isotopic dilution‐mass spectrometry (ID‐MS), and instrumental activation analysis (differences of 4 to 16% in relation to the unweighted mear for different techniques).