Determining What Percentage of the DryFlo Bed is Occupied by the Sample in the GeoPyc Envelope Density Analyzer

Poor reproducibility of results will occur if the GeoPyc® Envelope Density Analyzer is used with too little sample. The instrument simply cannot distinguish between a DryFlo® bed containing a sample and one without a sample when the sample volume occupies a very small percentage of the total bed.

New Capability for GeoPyc

For maximum performance, the sample must occupy at least 20% of the DryFlo bed. A larger percentage of the sample is preferred, as long as it is adequately surrounded by DryFlo. In order to make the sample percent visible, Micromeritics has incorporated a calculation for the percent of bed volume occupied by the sample into version 2.00 of the GeoPyc software.

In order to utilize this capability, each sample cell has to be calibrated without DryFlo or sample to establish the “zero bed” volume. This data is stored internally and the percent sample volume is reported with each analysis. This number can then be used by the operator to enhance the quantity of sample required to adhere to precise reproducibility criteria.

The following table and graph display the standard effect of sample quantity on the reproducibility of results. The sample used in this example was made up of diverse quantities of nonporous glass spheres measuring 6 mm in diameter. A 25.4-mm diameter sample cell was used to perform the analysis.

Micromeritics’ AccuPyc 1330 was used to measure the absolute density of the spheres that was 2.5202 g/cm3. As the spheres were nonporous, their envelope density was also 2.5202 g/cm3. As shown, this value is obtained within 1% when the sample occupies over 7.5% of the total bed volume. Although other materials will display similar behavior, they may not have 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
18.335 2.5089 -0.45
18.706 2.5155 -0.19
20.333 2.5153 -0.19
29.708 2.5289 +0.35

This information has been sourced, reviewed and adapted from materials provided by Micromeritics Instrument Corporation.

For more information on this source, please visit Micromeritics Instrument Corporation.

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