43
16. After plating for 120 min. at 0.5 amperes, the plating solution
is made basic with one to three ml of concentrated NH40H. After
one minute the plating cell is removed, disassembled and the
disc is washed sequentially with distilled water, acetone and
finally flamed to a dull red color over a bunson burner.
4,2-2
Chemical procedures for isolating polonium-210.
Polonium-210 was determined by spontaneously plating the
polonium out of 0.3 M HCL onto silver discs (Beasley, 1969).
of
208
Pu was used for the chemical yield determination.
A known quantity
The procedure is as
follows:
Chemical Procedures for the Separation and Platingof
Polonium from Coralline Sediments
1. An aliquot of dissolved sediment is spiked with a known
activity of
208
Pu and evaporated to dryness.
2. The residue is completely converted to chlorides by repeatedly
adding distilled 6 M HCL and evaporating to dryness.
3. The residue is dissolved in about 250 ml of 0.3 M HCL
(acid and water were both distilled in the laboratory).
4.
Reagent grade ascorbic acid is slowly added to the solution
until all the iron in solution is complexed, as is judged
by the disappearance of any yellowish color, then a small
additional amount is added.
5.
Polonium is spontaneously plated onto silver discs (one
side of the disc is coated with glyptal) by stirring the
n
solution in which the silver disc is suspended overnight.
. The silver discs are removed and lightly patted dry after
a distilled water rinse.
The side not covered with the
glyptal is alpha-counted.
4.2-3
Instrumentation of calibrations
The measurement of radioactivity by alpha spectroscopy
pra
was made by using eight 300 mm2 ORTEC®? silicon surface barrier diodes. Each
a. ORTEC, Inc., Oak Ridge, Tenn.
37830.