Date:         Thu, 1 Nov 2001 12:04:15 -0800
Reply-To:     Matthew Pollard <poll7356@UIDAHO.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Matthew Pollard <poll7356@UIDAHO.EDU>
Subject:      measuring pressure inside of a propane tank?
Content-Type: TEXT/PLAIN; charset=US-ASCII

My thermodynamics says that you can measure the pressure by mass. Weight
an empty tank and a full tank. The difference is the mass of the propane
in there. Now comes some math...
pressureXvolume=molesXgas constantXtemp
you know v, n, r, and t.
n=moles= mass of gas/formula weight of gas (propane is 44grams/mole)
v=volume of the clinder. Lets say 1L
R=gas constant=0.0821 L*atm/mol*Kelvin
Temp=298K (or about room temp).

So for 1000grams of gas, that corresponds to.... 556atm which is about
8173 psi. Yikes. that is high. Hmmm, somebody check my math here.

This is for an ideal gas though.... Propane is NOT ideal, esp at high
pressures. We'll need the van der waals equation for a better answer.

But that gives you an idea that we have a lot of pressure here!

ok, back to work
m

Matthew Pollard          "Racing with the wind and flirting with death
Dept. Of Chemistry        So have a cup of coffee and catch your breath"
University of Idaho
www.uidaho.edu/~poll7356