26
Yield
A comparison of the carrier and tracer yield measurements are
shown in Table 4.
These data were selected to show wide ranges of
recovery, yet in most cases, the strontium-90 yield (determined by the
tracer method) is better than 75%.
In those cases where the gravimetric
yield is higher than the tracer yield, it is assumed that macro amounts
of stable strontium have been leached from the soil.
On the basis of
many other soil samples analyzed at HASL, it can be said that the
strontium recovery is generally better than 80%.
The majority of the
loss apparently occurs in the oxalate precipitation, for in following
separations, only relatively small amounts of strontiumare lost by
either coprecipitation or incomplete precipitation.
For example, with
the tracer, it was possible to determine the percentage of strontium-90
which is coprecipitated with barium as the chromate.
Under the
conditions of this separation, a very small and consistent amount of
strontium is lost at this point.
Im the eight cases tabulated in
Table 4, the range is 107 to 2.4% coprecipitation.
Since the
gravimetric yield of strontium is determined by weighing the carbonate
precipitate, « study was made of the efficiency of this precipitation.
It was shown that under the conditions used in the procedure reported
here, the precipitation is quantitative,
Ta test the yield under the highest calcium concentration
expected, 30 grams of calcium as the nitrate were spiked with
stromtian-f2 co.er and 200 milligrams of strontium carrier eaddedo