Theory - Micromeritics AccuPyc II 1340 Operator's Manual

AccuPyc II 1340
This appendix provides theoretical information on the analysis function for the AccuPyc.
10-, 100-, and 350-cm
The AccuPyc is a gas displacement pycnometer which measures the volume of solid objects of
irregular or regular shape whether powdered or in one piece. A greatly simplified diagram of
the instrument is shown below.
Assume that both V
and that the valve is then closed. V
balance equation across the sample cell, V

P V
1 CELL
where
n = the number of moles of gas in the sample cell
C
R = the gas constant
T = the ambient temperature
a
The mass equation for the expansion volume is
P V
a EXP
where
P = ambient pressure
a
n = the number of moles of gas in the expansion volume
E
When the valve is opened, the pressure falls to an intermediate value, P
equation becomes

P V
2 CELL
June 2013
C. THEORY
3 Units
Calibrated Sample
Cell Volume
V
CELL
V
SAMP
and V are at ambient pressure P
CELL EXP
CELL

– V = n RT
SAMP C a
= n RT
E a

– V + V =
SAMP EXP
Calibrated Expansion
Valve
, are at ambient temperature T
a
is then charged to an elevated pressure P
, is
CELL
n RT + n RT
c a E a
Appendix C
Volume
V
EXP
. The mass
1
(1)
(2)
, and the mass balance
2
(3)
,
a
C-1