Re: Weight of compressed air.

[Brian Whatcott <inet@INTELLISYS.NET>]

Browsing the web accessible materials on Van der Waals equation, I was
amused to come across this message from MSU (in cached HTML format) - a
message to live by.

<http://google.com/search?q=cache:0Xi2guUJ7OgC:www.egr.msu.edu/~lira/errata/pg218.pdf+Van+der+Waals+equation&hl=en>


"The fact that the van der Waals equation still provides the basis of
modern engineering equations of state is a testimonial to the utility of
simple physical reasoning in engineering analysis. With a little effort,
you can learn from van der Waals' example."




At 03:42 AM 3/8/02, Ludwik wrote:
> Shawn Knudsen wrote:
>
> > Quick question for everyone out there.  I am looking for the weight of air
> > in a container that is pressurized to 80 psi.  The container is a cylinder
> > that is 1 foot in length and 9 inches in diameter.  I am not concerned
> about
> > the weight of the container itself.  How well does Boyle's Law hold for
> air?
>
> The Van der Waals equation constants for nitrogen are a=0.14
> and b=39.1 of SI units. Compare what that equation gives you
> with what Boyle's equation gives at different pressures to get
> the answer. Air probably behaves like pure nitrogen, in the
> first approximation. As you probably know, a and b are
> empirical constants describing real gases.
> Ludwik Kowalski

Brian Whatcott
  Altus OK                      Eureka!