C Sample Volume Equation Derivation
where
P
a
= ambient pressure
n
x
= moles of gas in the expansion volume
When the valve is opened, the pressure falls to an intermediate value, P
2
, and mass balance yields:
(3)
Substituting from equations (1) and (2) into (3):
(4)
or
(5)
then
(6)
Adding and subtracting P
a
in the denominator and rearranging gives
(7)
Dividing by (P
a
- P
2
) in both the numerator and denominator
(8)
or
(9)
C - 2
AccuPyc II 1345 Operator Manual
134-42851-01 (Rev A) ā Jan 2021