The Concentration & Partial Pressure at Criticality
To get the mass concentration at criticality then equation 6 needs to be rearranged. This results in the following equation.
![[Mass concentration at criticality]](images/equations/8.gif)
Where ![[Greek letter rho * C]](images/equations/rhocp.gif){kind=small}
=
mass concentration at criticality (kg/m3).
The pressure at criticality is defined as.
![[Pressure at criticality]](images/equations/9.gif){kind=small}
| Where | Pc | = Partial pressure at criticality |
| W | = Molecular weight (kg/kmol) |
Combining equation 8 with equation 9 and also using the molar heat of reaction as WQ = q* (J/kmol), then the following equation is derived.
![[Resultant of above description]](images/page12/equation1.gif)
This equation can be re-written, into the form of the straight-line equation (y = gradient*x + y-intercept).
![[Critical pressure equation]](images/equations/10.gif)
Equation 10 - Critical pressure equation
This allows a plot of a straight line graph to be made.
![[Straight line graph made using equation 10]](images/figures/5.gif)
This allows for a given vessel with physical parameters of a surface area (S), a volume (V) and convection coefficient (h), along with given chemical parameters of molar heat of reaction (q*), pre-exponential factor (A), and activation energy (EA), to be able to predict the partial pressure which is needed at ambient temperature to achieve criticality.