Masayuki Tabushi

The Half Life of Tb

A sample of Gd/sub 2/O/sub 3/ was borabarded for four hours with 38.5- Mev alpha particles and the activity of Dy/sup 157/ produced by the ( alpha ,3n) reaction was separated from the target material. Terbium was separated from dysprosium by an ionexchange method. The decay rate of Tb/sup 157/ nuclei was determined from the counting rate of the K x rays in a well type crystal, and the K and L electron capture ratio was measured using a NaI(Tl) crystal covered with Al, corrected for absorption by the Al cover, self absorption, photopeak efficiency, and fluorescence yield. The half life of Tb/sup 157/ was estimated at 160 ction in DDT-C/ 40 yr; a decay mode was proposed. (C.E.S.)

Decay of 150Eu

Abstract Carrier free sources of 150Eu were prepared from bombardment of enriched 150Sm with 11 MeV deuterons and 9 MeV protons. The half-life was determined to be 12.79±0.08 h. The maximum energy of the negatons was 1.02±0.01 MeV and the Kurie plot showed almost an allowed shape. However, the experimental shape factor showed a slight deviation from the allowed one. This decay was estimated to be 0− or 1− to 0+ transition. Positons with a maximum energy of 1.8±0.3 MeV and an intensity of about 0.3% and the K X-ray following orbital electron capture with an intensity of 3.9±0.2% were found. In scintillation measurements 15 gamma rays were observed. Gamma gamma coincidence studies were performed at several gate windows for gamma rays and annihilation radiations. The decay scheme of 150Eu was constructed on the basis of these results.

Decay of 157Tb

A sample of Gd2O3 enriched to 97.01% in the mass number 156 was bombarded with 38.5 MeV alpha-particles. The activity of 157Dy produced by the (α, 3n) reaction was isolated chemically from the target material. The number of nuclei of 157Dy was determined from the counting rate on the 330 keV photopeak. After the 157Dy radioactivity (T12 = 8.2 h) had died out, terbium was separated from dysprosium. The scintillation spectrum of the terbium fraction showed only one photopeak at the energy of 43 keV X-rays of gadolinium when the source was situated inside a well-type crystal. The number of 157Tb nuclei was determined from the counting rate of the K X-rays in the well-type crystal and by the measurement of the K and L orbital electron capture ratio with a thin NaI(Tl) crystal. From the number of nuclei of the parent and the daughter, the half life of 157Tb was estimated to be 150±30 y. A decay scheme of 157Tb is proposed.

Spectrophotometric determination of palladium with pontachrome azure blue b

Abstract A new spectrophotometric method for the determination of palladium with pontachrome azure blue B (Color Index 43830) as reagent is described. The palladium complex has maximal absorbance at pH 5.2–5.7 and at 605 nm. Beers law is obeyed up to at least 2.5 p.p.m. of palladium; the molar absorptivity is 4.79· 10 4 1 mole -1 cm -1 and the sensitivity is 2.2·10 -3 μg Pd cm -2 . The mole ratio of palladium and reagent in the complex is estimated to be 1:2. The formation constant of the complex is 5.0·10 10 under these conditions. Only copper(II) and iron(III) interfere with the determination of palladium when sodium fluoride is used as a masking agent.

SOLVENT EXTRACTION SEPARATION OF SCANDIUM FROM YTTRIUM AND RARE EARTH ELEMENTS

The solvent extraction separation of Sc from Y and rare earths with acetylacetone or dibenzoylmethane was studied. In order to find out a convenient method, the above methods were compared with conventional thiocyanate method and TTA method. The extractability was determined radiometrically, using radioactive isotopes, Sc/sup 46/, Y/sup 91/, Eu/sup 152 and Lu/sup 177/ as tracers. The last two elements were selected as the representatives of rare earths. The extraction recoveries of scandium obtained under each optimum condition are given. From the results it was revealed that both the acetylacetone- and dibenzoylmethane-benzene (or chloroform) systems are as usefui as the TTA-benzene system. Among them the extraction with acetylacetone or TTA is convenient as far as the separation of Sc from Y and rare earths is concerned. However TTA is better than acetylacetone, because the extraction can be performed at lower pH region. (P.C.H.)

Spectrophotometric Determination of Beryllium with Acetylaceton. Application to Aluminium-alloy

ベリリウムをアセチルアセトン塩としてクロロホルムで抽出分離し,その295mμ における吸収を利用して光度定量する場合の条件につき検討した,ベリリウムを10%EDTA溶液1～2ml,塩化ナトリウム2・5gを含むpH7～8の溶液からアセチルァセトン塩としてクロロホルムで抽出する。クロロホルム層のアセチルアセトンの過剰を水酸化ナトリウム溶液で洗浄除去したのち,ベリリウムのアセチルアセトン塩の吸光度を測定してベリリウム量を求める・本法により0.2～4μgのベリリウムが定量でき,ベリリウムに特異的で,多量のクロム,チタン,アルミニウムなどが妨害するに過ぎない。本法をアルミニウム申の微量のベリリウムの定量に応用して満足すべき結果を得た。