Takabumi Sakamoto

Spectrophotometric determination of uranium(VI) in phosphoric acid by means of solvent extraction with mixtures of TOPO and biphenyl

The variations in the distribution coefficients of twelve metals and uranium between nitric acid or hydrochloric acid-TOPO (trioctylphosphine oxide) systems have been studied as functions of the concentration of nitric acid, hydrochloric acid and TOPO and temperature (in the range 70–80 °C), employing biphenyl as the diluent for TOPO. The formula UO2(NO3)2-(TOPO)2 can be assigned to the complex. Uranium in a phosphoric acid solution is quantitatively extracted from 2 mol dm–3 nitric acid into molten TOPO-biphenyl at about 70 °C. The organic phase separates out as a solid on cooling and is dissolved in ethanol. The uranium in this solution is then determined spectrophotometrically with 1-(2-pyridylazo)naphth-2-ol. Beers law holds in the range 1–8 p.p.m. of uranium, and the relative standard deviation for 10 determinations was 2.1%.

Some problems on chemical composition analysis of clay minerals by analytical transmission electron microscope.

Chemical compositions of kaolinite, crocidolite, chlorite, sepiolite, chrysotile, beidelite and montmorillonite were analysed by analytical transmission electron microscope (AEM) and were compared with their bulk compositions measured by wet chemical method. Most of the data by AEM using approximately 10 nm probe size showed apparently richer in SiO2 than those by wet chemical method. No significant influence by K-factors of water was recognized by the comparison of the data of kaolinite and metakaolinite, which was prepared by dehydration of kaolinite. Data by picture mode for approximately 0.2μm×0.2μm region for kaolinite showed in good agreement with ideal composition whereas data by spot mode analysed in the same region showed apparently SiO2 rich composition, and were scattered very widely among particles. This anomaly in spot mode data was considered to be due to the channeling effect and possibly to the contamination and/or damage for the specimen by the incident electron beam.