Search Results

You are looking at 1 - 10 of 12 items for

  • Author or Editor: H. Honda x
  • Refine by Access: All Content x
Clear All Modify Search

Enthalpy increment HT-H289K measurements have been made on iron Chevrel phase sulphide Fe2Mo6S7.8, in the temperature range 300 to 500 K by the drop method using a hightemperature Calvet-type twin calorimeter. The first-order phase transition of this sulphide from a triclinic (low-temperature phase) to a rhombohedral (high-temperature phase) occurred at 375 K, and the enthalpy was evaluated to be 6.0 kJ/mol. The heat capacities of iron Chevrel phase sulphide Fe2Mo6S7.8 were also calculated before and after the phase transition.

Restricted access

Abstract  

Hot spring water samples have been analyzed for their rare earth elements (REE's) determination by the nondestructive neutron activation method. Five REE's, La, Ce, Sm, Eu and Yb, have consequently been detected and determined with satisfactory precision. The method has been found to be simple and suited for the simultaneous analyses of several samples. To determine all the REE's, however, some pretreatment of the samples will be necessary.

Restricted access

Abstract  

Neutron activation analysis was successfully applied to the determination of Th and U at ppt levels in a neutral hot spring water. Blank test corrections were found to be essential to reach the final determined values. Normal NAA is a better method for the Th determination than epithermal NAA, while both NAAs are nearly equally effective for U determination.

Restricted access

Abstract  

Determination of Th and U in acidic hot spring and crater lake waters was investigated by neutron activation analysis (NAA). Before neutron irradiation, Th and U were preconcentrated and separated from interfering nuclides such as alkali metals and halogens by coprecipitation with aluminium. Irradiation was carried out in two ways, viz., irradiation with Cd foil wrapping (epithermal NAA) and irradiation without Cd foil wrapping (normal NAA). The final determined values of Th and U were at ppb levels. Higher reliability of the determined values was obtained for Th than for U. It was found that epithermal NAA was more effective for the determination of these two actinides than normal NAA and was more effective for the determination of U than that of Th.

Restricted access

Abstract  

Determination of the lanthanoids in a neutral hot spring water has been studied by menas of neutron activation analysis. The aluminium coprecipitation process, which used aluminium as the collector of the lanthanoids, was incorporated in the preparation of a sample for irradiation. Nine lanthanoids, La, Ce, Nd, Sm, Eu, Tb, Tm, Yb and Lu, were determined at ppt levels with satisfactory precision, indicating the effectiveness of aluminium coprecipitation.

Restricted access

Abstract  

Determination of the lanthanoids, thorium and uranium in silicate rocks has been investigated by neutron activation analysis (NAA). Seven or eight lanthanoids and thorium and uranium were determined by non-destructive instrumental NAA. The numbers of the lanthanoids determined were increased and errors on the final values were reduced by pre-irradiation treatments, which included a coprecipitation process with aluminium as collector to remove the alkali metals and halogens and a solvent extraction process to eliminate iron. The necessity of scandium removal was indicated.

Restricted access

Abstract  

Determination of the rare earth elements (REE's) in acidic hot spring and crater lake waters by neutron activation analysis (NAA), in which activation was performed mostly by epithermal neutrons (epithermal NAA) was investigated. Nine REE's, La, Ce, Sm, Eu, Tb, Ho, Tm, Yb and Lu, out of fourteen naturally existing REE's were determined at ppb levels with satisfactory precision. The epithermal NAA was found to be more effective in the determination of Sm, Tb, Ho and Yb than normal NAA, in which activation was performed mainly by thermal neutrons. Combined use of the epithermal and normal NAA's enabled the determination of eleven REE's, La, Ce, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb and Lu.

Restricted access

Abstract  

Hot spring water and crater lake water samples were analyzed for their rare earth elements: (REE's) by neutron activation method, which, in the irradiation, sample preparation, incorporated a coprecipitation process in which aluminium was used as a collector. Ten REE's, La, Ce, Sm, Eu, Gd, Tb, Dy, Tm, Yb and Lu, were consequently detected and determined at the ppb level with satisfactory precision. It was shown that the aluminium coprecipitation is effective in enhancing concentrations of the REE's and reducing the amounts of interfering nuclides before neutron irradiation.

Restricted access

Abstract  

Previously undetermined three rare earth elements (REE's), Pr, Nd and Er, in acidic hot spring and crater lake waters were determined at ppb levels by neutron actavation analysis with the standard addition technique. Errors on final detemined values were 7.1–56%. Combining the present results and the results previously obtained amounts to the determination of all 14 naturally occuring REE's in the waters.

Restricted access

Abstract  

We present a brief description of the status of our accelerator mass spectrometry system at the tandem accelerator facility of the University of Tokyo and some examples of measurements in environmental samples which have been recently performed. Fallout10Be activities have been measured, from rain samples collected monthly in Tokyo from 1975 to 1977 and from 1984 to 1986, and compared with those of7Be and137Cs. A preliminary experiment on14C measurement in volcanic gas samples is also reported.

Restricted access