graph of a pressure ratio

[werka]

I have an equation that is basically

Permeability = Constant/time x ln (Pressure ratio)

Pressure ratio is:
(Pressure Outside- Pressure at some time)
divided by
(Pressure Outside - Pressure initial)

Anyhow, when I am interested in obtaining a value of the permeability. I have data showing pressure differences with respect to time. If I graph the ln of the Pressure Ratio with respect to time what will this tell me?

Any other help is appreciated.

 

[borgwiser]

Rearrange the equation slightly. It's a little tough without making explicit assumptions on the order of your operations, but I'm going to assume your equation is:

Permeability = (C/t) x ln(Pressure Ratio)

So, rearrange to:

t = (C/Permeability) x ln(Pressure Ratio)
If C and Permeability are constants, then the slope of this line (it will be a line) is C/Permeability. Solve for Perm.

 

[werka]

The main problem is that permeability depends on the partial pressure.

My setup is basically a milk carton with water in it. I have purged the dissolved gases out of the milk carton. Over time the milk carton leaks (permeable) the dissolved gases back in (oxygen is what I measure). I have data showing dissolved oxygen readings with respect to time. It is not linear.

So if I graph the ln (Pressure Ratio) vs. time, does this info give me any useful info.

Using the equation that I listed:

Permeability = Constant/time x ln (Pressure ratio)

My data is as follows:

Recorded Data
Net Time Temperature Permeability
(hours) (C)
0.27 21.3 2.58E-18
0.47 21.4 2.13E-18
19.98 23 3.25E-19
38.22 25 1.87E-19
61.97 25 2.18E-19
89.38 23.7 2.59E-19
121.80 22.7 3.20E-19
161.30 25.3 3.29E-19
190.30 22.9 4.26E-19
213.05 23 4.87E-19