TABLE 5.2
Predicted vs Observed Particle Size Separztions by Stendard Steves
Size Range of Sieves
(i)
Wh§3
53-62
62-74
74-88
88-105
105-125
125-149
145-177
dy
Number of Particles
_(y
Counted
62.4
85.8
79.5
113
116
172
215
239.
321
228
32?
369
150
181
381
286,
The frection from the 62-74 i sieve had a particularly broad
distribution, so that all data associated with it should be viewed
“ale
with great suspicion.
The Roller analyzer, used here for particles smaller than 50 p,
provides sharper size separations less sensitive to particle shape
than the sieves.
On the other hand it is more likely to break up
frangible or agglomerated particles. A comparison of celiorated size
with observed size is given in Table 5.3.
ARLE 5.3
Predicted vs Observed Particle Size Separations by Roller Analyzer
Calibrated ©
Size Range
()
5-10
- 10420
20=30
30-40
dy
Namber of
(py)
Particles
Counted
10.3
3.3
29.5
43,7
743
376
1089
429
From recent autoradiographic studies it has been found that the
experimental determination of the per cent active particles in the
lower size range may require a correction under certain conditions.*®
This results from experimental limitations as to the size and specific
activity of a particle which mey be detected as hot.
*This discussion of autoradiograph errors is due to Mr. Robert J.
‘French of these Laboratories.
38
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