2aoe
5. Filter in Fisher Filtrator using Whatman #41 or 42 filter paper. Record timeoffiltration.
6. Wash precipitate with distilled water.
7. Remove and store filtrate for later milking.
8. With a clean beaker in thefiltrator and the vacuum off, fill the funnel containing the
precipitate with hot 50% HCl. Allow to stand for about 1 minute to dissolve the precipitate
and then pull through by turning on the vacuum. Repeat this procedure to thoroughly dissolve
precipitate from paper.
9. Wash paper with distilled water.
10. To the filtrate, carefully add concentrated NH,OH with vigorous stirring until precipitate
just appears,
11. With continued stirring add concentrated HCl dropwise until precipitate just dissolves.
12. Add concentrated oxalic acid in excess. The white oxalate of yttrium should appear.
13. Digest with heating for about ten minutes.
14. Filter in Fisher Filtrator using Tracerlab precipitation funnel and Whatman #42, 1%”
diameter paper.
15. Dry by allowing vacuum to pull on paper for about five minutes.
16. Carefully remove paper and fit on Tracerlab brass disk.
1%. Cover with pliofilm and secure with brass ring.
18. Note sample number on bottom of brass disk.
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Check pH at the end of this time.
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4. Digest with heating for about ten minutes.
be between 1.0 and 1.5 for best results.
F. Details of counting equipment:
The new counting system designed for project SUNSHINEis pictured in Figure 1, with the
outer housing and lead shielding removed. In use, the lucite counter housing seen in front of
the main unit is within the anticoincidence ring and moves out for sample changing by sliding
along the tracks seen at the open end of the ring.
The actual counter utilized is an Anton flat Geiger counter model No. 1007 with a 1 inch
diameter mica window. The counter is seated within the lucite housing and power is supplied
through the single cable which is wired at its other end to the front amphenol connector on the
base. Careful machining of the lucite has resulted in the mica window of the counter being at a
constant distance of about 2 millimeters from the top of the sample.
The samples which are mounted on brass disks fit into the receptacle in the lucite slide of
the housing. A stop on the slide seats the sample accurately under the counter window when
the slide is pushed in as far as possible.
Cosmic ray shielding is accomplished by means of the ring of cosmic ray counters in anticoincidence with the sample counter. The tubes employed are Radiation Counter Laboratories
Model 52-12 cosmic ray counters. The overall lengths of these tubes are 1514 inches, the active.
anode length is 12 inches. The pig tails on the far end of these tubes are connected in parallel
by a copper ring which is in turn connected to the rear amphenol connector seen in the figure.
In counting position, the lucite housing is seated in the center of the A.C. ring, the long
handle projecting about 2 inches from the front of the unit. By merely pulling the handle, the
sample slide moves forward and the lucite housing emerges from the ring. Sample changing
is thus a rapid and simple procedure, neither cables to be disconnected, nor voltages turned down.
The plateau for this counter has been found to be about 100 volts long with a slope of about
1% per volt. Optimum operating voltages are 625 volts on transmit and 900 volts on reject.
The background of 2 counts per minute has been constant for about 2 months since the counter
has been built.
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