Micromeritics AccuPyc 1330, Operator'S Manual, Page: 97 / 115

CALIBRATION THEORY
Prior to running samples on the AccuPyc 1330 Pycnometer, the volume of
the sample cell and the expansion volume must be known. The derivation
that follows permits these internal volumes to be measured with respect to a
removable, accurately known standard volume. A simplified diagram of the in-
strument is shown in Figure C-1.
Assume that, V
CALIB
is removed, V
CELL
is charged to an elevated gauge pres-
sure P
1
and V
EXP
is at zero gauge (ambient) pressure but sealed and that the
valve is closed. Upon opening the valve, the condition established is
P
1
V
CELL
=
P
2
(
V
CELL
+
V
EXP
)
(1)
where P
2
is the resulting intermediate pressure. The use of gauge pressures is
permissible because it is equivalent to having subtracted a constant from both
sides of the equation.
Figure C-1. Simplified Diagram for Calibration
Placement of V
CALIB
into V
CELL
and repetition of the charging and expansion
yields
P
1
∗(
V
CELL
−
V
CALIB
) =
P
2
∗ (
V
CELL
−
V
CALIB
+
V
EXP
)
(2)
Where P
1
* and P
2
* are the before and after expansion pressures with V
CALIB
in place.
Expansion Volume
V
EXP
Sample Cell Volume
V
CELL
V
CALIB
Valve
AccuPyc 1330 APPENDIX C
September 1996 C-1