On Wednesday, May 10, 2017 at 11:31:19 AM UTC-4, wrote:
On Monday, May 8, 2017 at 7:57:30 PM UTC-4, Neon John wrote:
On Sat, 6 May 2017 14:21:09 -0700 (PDT), wrote:


That was my suggestion. Ideal gas law.
P*V=N*k*T. I think you could just use compressed
air. As long as you know the tank volume on your
compressor and have a good pressure gauge.
(T is in Kelvin)

You absolutely can NOT use the ideal gas law because none of the
gasses are ideal. The Van der Walls equation must be used. Learn all
about it he

https://opentextbc.ca/chemistry/chap...-gas-behavior/

Sure I learned that in my physics thermo classes.
(Helium is pretty close to idea... but spendy)
For a rough measure of volume (a few percent) I think air will be fine.
Temperature might be a bigger uncertainty.

George H.

John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

Once again for all concerned (and I am overwhelmed and thankful for all the responses), We're not buying this stuff by the teaspoonful. It will be delivered in 800 pound (net) and 110 pound (net) tanks. I can return what I don't use. I'm really just trying to get a reasonable ballpark number to order with.

I expect to be running this test Saturday, so stand by for results.