Micromeritics AccuPyc II 1340 - Gas Displacement Theory for 1-cm3 and 2000-cm3 Units

AccuPyc II 1340 Appendix C
June 2013 C-3
and equation (9) rewritten as
(12)
Equation (12) then becomes the working equation for the pycnometer. Calibration procedures
are provided to determine V
CELL
and V
EXP
and the pressures are measured by a gauge pressure
transducer. Provisions are made for conveniently charging and discharging gases at controlled
rates, for optimizing the relative sizes of the sample chambers and expansion volumes, and for
cleansing the samples of vapors.
1-cm
3
and 2000-cm
3
Units
The 1-cm
3
and 2000-cm
3
pycnometer operate by filling the expansion chamber while the sam-
ple cell remains at ambient pressure. After P
1
is equilibrated, the expansion valve opens to
allow gas to expand into the sample chamber and P
2
is equilibrated.
For the 1-cm
3
pycnometer, equation (1) becomes
and equation (2) becomes
A derivation similar to that above yields the working equation for the 1-cm
3
pycnometer.
V
SAMP
V
CELL
V
EXP
P
1g
P
2g
--------
1–
-------------------
–=
P
1
V
EXP
n
E
RT
a
=
P
a
V
CELL
V
SAMP
–n
C
RT
a
=
V
SAMP
V
CELL
V
EXP
P
1g
P
2g
--------
1–


–=