THE RADIOCHEMISTRY OF PLUTONIUM - Sciencemadness.org

10.
11.
12.
13.
14.
15.
16.
17.
16.
19.
20.
21.
Add to the solution in the upper funnel 0.1 mg Fe+++ and 2 ml of a 5%
cupferron solution, shake, and let stand for 45 min.
Repeat the whole extraction procedure twice (8 and 9) with 25 ml of purified
chloroform. Transfer the water-layer resulting from the first repetition
from the lower to the upper funnel. Discard both water-layers in upper and
lower funnel after the second repetition.
Wash down the sides of the two filter papers into the roundbottom flask with
as little chloroform as possible to remove traces of red-brown iron- cupferrate.
Distill off the chloroform until about 20 ml is left and remove the remainder
of chloroform by gentle blowing or suction, afi shown in Fig. 59.
Add 1 ml of concentrated suJfuric acid (C. P. grade) and attach to the round-
bottom flast a 15-cm condenser. Reflux for 30 min.
Add 2 ml of fuming nitric acid (C. P. grade) and heat until the solution
appe~s light yellow.
Remove nitrous vapors and sulfur trioxide first by heating, later by
sucking air through an attachable tube, creating slight turbulence in the
bulb and the neck of the roundbottom flask. Two burners should be used,
one to keep the bulb hot, without heating the dry residue to a red glow,
however; and the other to prevent condensation in the neck of the round-
bottom. If the dry residue does not appear snow-white after cooling,
repeat 14 and remove sulfur trioxide by heating as above.
Dissolve the white residue in 1 ml of concentrated HCL while gently
heating. Some time may be needed before the solid is completely dis-
solved.
The final sample for counting is deposited on a Pt tray of 35 mm diameter
and 1/8 cm thick. Determine the counter background with the tray in
counting position. Place the tray under a radiant heater and, using a
drawn-off pipette, transfer the green-yellow solution onto the tray,
covering about half of the area. Rinse the flask with a second ml of con-
centrated HCL and transfer the washing onto the tray. Repeat with 1 ml
of water. After evaporation to near dryness, add a few drops of water.
Enclose the tray and two 10-ml beakers filled with 10-15~0 ammonia in a
large beaker upside down. Let stand for at least 5 min to ensure the
formation of Fe(OH)3 to be completed, Evaporate to dryness.
Place the tray in a porcelain dish, cover it with a second dish, and ignite
for 10-15 min to convert the hydroxides to oxides.
Count the sample under an a-counter. A simple counting device consisting
of a photomultiplier and a ZnS screen, provided with a light trap for insert-
ing samples without switching off the high voltage, showed to be very re-
liable and satisfactory. Efficiencies up to 47-50 percent may easily be ob-
tained. Calculate the Pu concentration according to the formula
c Pu = 9.01 X 10-s ~pc/ml
where A = activity of sample in counts per minute and E = percentage
efficiency of counter.
138