RESUMO
The coulometric electrolytic principle is utilized for the measurement of moisture sorbed on sintered thorium dioxide. Moisture is removed from the sample by heating and is swept by dry argon gas through a hygrometer. The resulting hygrometer output is converted into frequency pulses and counted cumulatively. The instrument is calibrated by use of standard hydrated chemicals. The number of counts/mu;g of water obtained from standards compares favourably with the theoretical number of counts/mu;g calculated from performance specifications of the components employed. The error is <5% for 1-350mu;g of water. A high sensitivity and low operating blank recommends application of this method to materials other than thorium dioxide, having very low moisture contents.
RESUMO
A method has been developed for the determination of helium produced during neutron irradiation of beryllium oxide ((9)Be + n --> (8)Be + 2n; (8)Be --> 2(4)He). The sample is dissolved by refluxing in a sulphuric acid-phosphoric acid mixture in an argon atmosphere. After the sample has completely dissolved, the released helium is transferred to a gas sampling bulb by means of a Toepler pump. An activated charcoal trap cooled by liquid nitrogen is used to separate helium from argon. The helium is determined by gas chromatography using a 20-ft Linde 5A molecular sieve column.
