and 2.30 reduces the influence on the standard of multiple neutron capcures on
12;
130
a7
I £0 produce
.
;
,
2
This standard was preoared in solution form so thar 1 to
I.
WM
19
:
Se
a
a
.
+O
ud »would produce
sufficient
activity for iodine activation analyses.
made from unknown amounts of NH,
27
2
I( 10g),
-
v
[t was
os
> (10 mCi) and from 0.1% of the
solution contained in an ampoule of (NBS) 129, Standard Reference Material
(SRM) number 4949 in 100 ml of aqueous solution.
.
os
aged 5 months ‘to eliminate any
126
.
I activity.
The 125, solution had been
,
a
The solution ccmposition per ut
at make-up is shown in Table I.
TABLE I
Composition or Comparator Standard
for Iodine Activation Analysis
The 123
I
20 dps/uzr
127,
87.5 ug/ur
129)
6.0 x to! atoms U2
1297 127,
1.45 x 107° atom ratio
127) 129, standard solution requires the addition of 123) (Ty,
= 60 davs) about once a year.
The added 123) is contained in less than 100 uz
tO minimize dilution of the standard.
Annually after the 125 I addition the com-
position of the standard solution is compared by activation analysis to that of
the older mixed elemental iodine standard,
measured aliquots of NBS-SRM-4949.
to the Cel, standard,
and to sealed
Sufficient sealed quartz irradiation
ampoules of the standard solution are then prepared for use over a year's time.
4
The mean 129,127, atom ratio of the original elemental iodine isotopic
Standard (nominal 2.1 x 1078 atom ratio) based on the standard solution isotopic