Micromeritics Gemini VII 2390a, Operator'S Manual

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Appendix B Gemini VII
B-14 239-42828-01 - Nov 2013
4039- The isotherm does not meet the constraints of the Cheng/Yang assumption.
Cheng/Yang correction will not be applied.
4040- The value of Qm computed from the Langmuir equation is too low. The pore
size will not be computed for all data points.
4041- Cheng/Yang correction is inappropriate for some P/Po .
Cause: The Cheng/Yang correction to the Horvath-Kawazoe equation
requires the value of the monolayer volume as calculated from the
Langmuir equation. The isotherm does not correlate to the Langmuir
assumption with a coefficient of 0.98 or more. The correction is not
applicable to this isotherm or to the range of the data points selected.
Action A: The analysis will be performed without the Cheng/Yang correction.
Deselect Apply Cheng/Yang correction on the Horvath-Kawazoe
Report Options window to prevent this message from appearing on
future reports.
Action
B: Generate the Langmuir report for the same data points selected for the
Horvath-Kawazoe report. If the Langmuir correlation coefficient can
be brought above 0.98 by removing some points at high relative
pressure, remove them and reproduce the Horvath-Kawazoe reports.
Cause: The Cheng/Yang correction to the Horvath-Kawazoe equation
requires the value of the monolayer volume as calculated from the
Langmuir equation. The computed value is less than the volume
adsorbed at the largest relative pressure included in the analysis. The
correction is not applicable to this isotherm or to the range of the data
points selected.
Action: The analysis will be performed and the Cheng/Yang correction will
be applied to all points with a volume adsorbed less than the value of
Vm. The pore size will not be calculated for data points with an
invalid volume adsorbed. Deselect Apply Cheng/Yang correction on
the Horvath-Kawazoe Report Options window to clear this message.
Cause: The Cheng/Yang correction is usually inappropriate for any P/Po
above the isotherm knee. In some instances, the computed pore sizes
may decrease above the knee. While it is possible to include these
relative pressures (usually above 0.1 P/Po) in the analysis, the
computed pore sizes for these pressures are usually meaningless.
Action: Change the data points selected for the Horvath-Kawazoe report to
include only relative pressures at or below the knee of the isotherm or
change the Horvath-Kawazoe report options so that the Cheng/Yang
correction is not applied.