2of
Interferences
Since the only elements which will precipitate with fuming
nitric acid under the conditions used in the procedure are calciun,
strontium, barium, radium, and lead, the potential radioactive inter=
ferences are radium and its daughters and barium-140 and its lanthanum
daughters,
Lead and Letho are scavenged in the first yttrium milking
end radium and barium are removed in the barium chromate precipitation
which immediately follows.
In one soil analysis, the precipitate from
the first milking was mounted and the activity followed over a period
cae
aery
fa
i
j
of 140 hours.
There was a rapid decay initially, then a leveling off
to a constant value after two weeks as shown in Figure 1.
This indicated
the presence of ppele, pp©10 end other shorter-lived radium daughter
products,
The level of activity after 4.0 hours was about the same as the
activity attributed to strontium-90 at equilibrium after the second
milkingo
Experience has shown that soil containing milligram quantities
of titanium, present analytical difficulties which are troublesome but
not critical,
This element invariably carries through the nitric acid
separations, and until it is completely removed in the ‘first milking’,
filtrations can be quite difficult and slow,
The titanium compound (its
chemical form is uncertain but there is evidence to indicate that it is
a titanoesilicate complex) does not appear to scavenge significant amounts
of strontium.
if the prevsaure in the Appendix is strictly adhered to, all
interferences are eliminated since a pure strontium fraction is obtained,
.
ss
—
.“NAS
~~
’
=