DRY FLO BED
If too little sample is used, poor reproducibility of results will occur. The instrument is unable to
distinguish between a Dry Flo bed with sample and one without sample when the sample volume
occupies too small a percentage of the total bed. For optimum performance, the sample should
occupy a minimum of 20% of the Dry Flo bed. A larger percentage of sample is preferable as long as
it can be surrounded sufficiently by Dry Flo.
Each sample cell requires calibration without Dry Flo or sample to determine the zero bed volume.
This information is stored internally and thereafter the percent sample volume is reported with each
analysis. This number can then be used to optimize the quantity of sample necessary to meet a
specific reproducibility criteria.
The following table and graph show the typical effect of sample quantity on the reproducibility of
results. The sample used in this example was composed of varying quantities of nonporous glass
spheres 6 mm in diameter. The analyses were conducted using a 25.4 mm diameter sample cell.
The absolute density of the spheres was 2.5202 g/cm3 as measured by Micromeritics’ AccuPyc
1330. Being nonporous, the envelope density of the spheres was also 2.5202 g/cm
3
. As shown, this
value is achieved within 1% when the sample occupies more than 7.5% of the total bed volume.
Other materials will exhibit similar behavior but may not follow this exact pattern.
%Sample Volume
Envelope Density %Error
0.537
2.8223 +11.99
1.228
2.5416 +0.85
1.284
2.4177 -4.07
1.299
2.3913 -5.11
1.944
2.3903 -5.15
3.012
2.5419 +0.86
4.782
2.5518 +1.25
5.761
2.5699 +1.97
7.523
2.5288 +0.34
9.616
2.5269 +0.27
12.547
2.5386 +0.73
14.063
2.5193 -0.04
15.538
2.5041 -0.64
18.039
2.5184 -0.07
Typical Effect of Sample Quantity on the Reproducibility of Results
Dry Flo Bed
GeoPyc 1365 Operator Manual
136-42800-01 (Rev -) — Dec 2016
7 - 5
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