-15-
lost in processing the pH. 6. 1 solution.
Identification of Europium-155
Unidentified gamma peaks of 0.044 Mev, 0.089 Mev, and 0. 108
Mev, were observed in the fourth aliquot of the pH 2. 8 fraction
(Fig. 6A).
The isotope contributing these peaks was identified as
europium-155, a rare earth isotope with a half life of 1.7 to 2.0
years. 10
A separation using standard radiochemical precipitation
techniques was made which showedthat 88 per cent of the radioactivity in this fraction was due to rare earth elements.
A gamma
spectrum of this separation, which is a duplicate of the one obtained
with the sample from the ion-exchange separation, is shown in
Figure 6B.
Further verification of the presence of Eu155 was obtained from
aluminum absorption curves which showed that the maximum energies
of the two beta particles from the sample were 0. 155 Mev and 0. 24 Mev.
These values are in agreement with the beta energies given for Eu!55
by Boehm and Hatch,
7
who cite 0. 16 Mev and 0. 24 Mev.
gr99. y90 Determination with Dowex 50
In the ion-exchange determination of gr80 the second elution with
ammonium citrate at pH 3.5 removed the Y99 daughter of Sr99 trom the
resin column.
Duplicate columns were used and the results of the two
Sr80 determinations are given in Table 3.