# Air solubility coefficient

1. Jul 31, 2007

### robsmith82

Hello,

How would I go about finding the air solubility coefficient of a kerosene based aircraft fuel? I know that as a rule of thumb, air pressure is close to percent dissolved air, eg. at atmosphere, 15 psi gives around 15% dissolved air, but how would I calculate the coefficient accurately?

2. Jul 31, 2007

### chemisttree

I would find the partial pressure of the liquid of interest at the temperature you are given. That may not be straightforward. From that partial pressure you can calculate the number of moles of liquid at that temperature using some form of the ideal gas law (IGL). There are several approximations or enhancements to the IGL that address non-ideal behavior. Multiply the moles by the average formula weight of the liquid to obtain the mass of vapor (assume kerosene?). The gas constant will indicate the units of volume which that mass occupies.

3. Jul 31, 2007

### robsmith82

Thanks for the reply.

Not sure how I can find the partial pressure. I can find the true vapour pressure from the reid vapour pressure if it is possible to do from this?

4. Jul 31, 2007

### chemisttree

It may be but I'm not sure how that might be done. Here is a thesis on the subject. I can't vouch for its accuracy.

http://www.ddbst.de/new/InfoMat/Yash_Nannoolal_Phd_Thesis_2007.pdf [Broken]

Since your liquid (kerosene or JP8) has a boiling range from 150C to 290C, data for a single substance may not be helpful. The thesis and references therein present methods to calculate pressures of more complex mixtures like this. After you calculate the partial pressure you still need to estimate the average molecular weight of the vapor mixture. I have no idea how to do that without some type of measurement.

Last edited by a moderator: May 3, 2017
5. Aug 4, 2007

### FredGarvin

You need to look into the Ostwald Coefficient.

6. Mar 8, 2008

### 273

robsmith82
Here you are.

The links below show the Ostwald coefficient for aviation kerosine in terms of volume of gas per volume of fuel (independent of pressure):

http://gp5.home.infionline.net/ost1.gif [Broken]
http://gp5.home.infionline.net/ost2.gif [Broken]

The data comes from:

"The Effect of Fuel on an Inert Ullage in a Commercial Transport Airplane Fuel Tank"
by William M. Cavage, July 2005,
DOT/FAA/AR-05/25 Office of Aviation Research Washington, D.C. 20591,
APPENDIX A—GRAPH OF OSTWALD COEFFICIENT FOR OXYGEN AND NITROGEN, page A-2.

Hope this helps.

Last edited by a moderator: May 3, 2017