Studies on the coulometric determination of uranium (VI) and Thallium CD by Controlled Potential Electrolysis

In recent years, coulometric analysis has been developed and widely used as a technique for the determination of substances in solution by measuring the quantity of electricity required for the completion of a reaction in an electrolysis cell. Of two coulometric techniques, i. e., coulometric titration with a constant current and coulometric analysis with a controlled potential of a working electrode, the latter is more interesting to the author, because by this method both electrolytic separation and quantitative determination of chemical species can be achieved simultaneously. Especially, the use of a mercury cathode as the working electrode(1)) has an advantage that the optimum control potentials can easily be determinable from polarographic data. In our laboratory, we took up the coulometry of uranium as one of the interesting themes of researches when we had an opPortunity in studying various kinds of analytical methods for uranium in accordance with the request by Japan Atomic Fuel Corporation. The coulometric determination of uranium (VI) by using a mercury cathode at a controlled potential was studied by G. L. Booman, W. B. Holbrook and ]. E. Rein(2)). It was found to be very useful for the analysis of uranium in a highly enriched nuclear element which underwent fission to an appreciable extent. But the instrument used by them(3)) was complicated and expensive. Therefore, a simple counter millicoulometer has been coustructed in our laboratory, a readymade potentiostat (electrical instrument for automatic controlled potential electrolysis) being tried for electrolysis. By these instruments, the author studied the fundam ental conditions of coulometry for uranium and tried the successive determinations of uranium and thallium in mixed solutions

The Role of Cattle Dung in Seed Dispersal of Major Species in a \u3ci\u3eZoysia japonica\u3c/i\u3e Pasture in Japan

To evaluate the role of cattle dung in seed dispersal of major species in Zoysia japonica pasture in Japan, we investigated the species composition and density of seeds in cattle dung by means of a germination test. Of 20 major species which had a mean coverage of more than 0.1%, 90% were detected as seeds in cattle dung. In addition, the species composition and density of seeds in cattle dung differed among three sampling seasons. Seeds of the six most prevalent species in terms of coverage were detected from cattle dung during the growing season. Hence, we conclude that it is possible for major species to invade other grasslands and pastures by means of cattle dung

SPECTROPHOTOMETRIC DETERMINATION OF ZIRCONIUM

Neo-Thorin was previously presented by the other authers as a color-developing reagent for the spectrophotometric determination of zirconium. 1) To determine the optimum condition for the use of this method, the effects of pH, time and temperature, and the interference of several ions were checked. The following conclusions were derived from the experimental results: Absorption curve-- The zirconium Neo-Thorin complex salt shows a maximum absorption at 580 mμ against Neo-Thorin (Figs. 1 and 2). Effect of pH-- The complex salt gives a maximum absorption at pH 1. 7 (Fig. 3). Effect of time and temperature-- Color absorption is stable for a period of 15 to 200 minutes after color development at room temperature. Heating over 40°C is harmful, because of the formation of a purple precipitation. Interference by several ions-- Cations UO(2)(2+) and Fe(3+) besides Th(4+), considerably interfer with color development. The absorption of 2000 μg U corresponds to that of 10 μg Zr (Fig. 4). However, interference by Fe(3+) becomes negligible if hydroxylamine hydrochloride is added. 2) As a result of the above conclusions, the following procedure is recommended: Procedure recommended-- A few ml of sample solution, 1 ml of 20% hydroxylamine hydrochloride and 1 ml of dilute acid, if necessary, are mixed and diluted to 9 ml. To this solution, 1 ml of 0.05% Neo-Thorin is added. The pH value of the final solution is 1.7. From 15 to 200 minutes after mixing, color absorption is measured at 575 mμ. In the range of 0 to 150 μg Zr per 10 ml, the color absorption of the complex salt obeys Beer's law (Fig. 5). 3) In demonstration, this method was applied to the determination of zirconium in a uranium mineral. Table 1 shows the zirconium content of beta-uranophane from Katamo Mine, Tottori-ken

CHEMICAL STUDY ON SEKIGANE HOT SPRINGS, TOTTORI-KEN

The chemical and physical characteristics of the thermal and ground waters in Sekigane Hot Springs were determined. The content of the following chemical constituents was determined: Cl(-), S0(4)(2-), HCO(3)(-), Ca(2+), As, F, U and Ra. The relationship between water temperature and depth of spring wens was found to be indicative of the presence of a fissure, in agreement with the conclusion reached geologically by Sugiyama. The water temperature, the e1ectricconductivity and the content of chemical constituents of the ground water were as expected markedly lower than those of the thermal water. As a whole, however, the water temperature, the electricconductivity and the content of SO(4)(2-), HCO(3)(-), Ca(2+), As and F are in positive and linear correlation with the Cl- content. In other words, these characteristics of the waters, excluding the U and Ra content, correlate positively and linearly with each other. This was interpreted to mean that a thermal water of high salinity is simply diluted by a cold ground water of very low salinity, and that a ground water of relatively high salinity is contaminated by thermal water. The content of U and Ra of these spring waters is lower than that of the spring waters in Ikeda, Shimane-ken, and Misasa, Tottori-ken, where radioactive springs also issue. Finally, it is concluded that As and F will be as useful as Cl- in chemically locating a new site for a spring well in Sekigane because of the low contamination due to human life of ground water by these elements

Studies on the Chemical Composition and Levels of Ground Water at Misasa Hot Springs

The water levels of the thermal springs and the ground water levels were measured and the contour of the water table was obtained. The contour was disturbed at two regions in which many springs issue. The thermal and ground waters were sampled all over the springs district, and the water temperatures were measured when they were sampled. The chloride, bicarbonate, sulfate, calcium and magnesium content was also determined. In addition, the analytical methods for the determination of arsenic, phosphorus and acid-soluble iron were improved. Also the concentration of these elements was determined. Based on the results of the observations and chemical analysis, the relations between the water temperatures and content of chemical constituent and the chloride content were checked respectively. Positive correlations were found in the relations between water temperature～Cl(-), HCO(3)(-)～Cl(-), SO(4)(2-)～Cl(-), Ca(2+)～Cl(-), and As～Cl(-). Furthermore, the regional differences were detectable in the ratios of water temperature to chloride content and of bicarbonate to chloride content, nevertheless the correlation as a whole were valid. The diversity and regional differences of the chemical composition of the waters were explained as due to the differences in the mixing proportion of the magmatic thermal water and the varying kinds of ground water at the deep site in the ground and at the site near the ground surfaces

口永良部島におけるサンゴ礁魚フタスジリュウキュウスズメダイの性転換と繁殖戦術に関する生態学的研究

内容の要約広島大学(Hiroshima University)博士(農学)Doctor of Agriculturedoctora