"Clark" wrote in message
...
A minor nitpick on a previous post from Jim:

snip

It was stated that n/V was equal to density. While the stated equality
isn't,
the jist of what was said was ok. The equality would be

(Mass/Molecular Weight)/V = density

Since the molecular weight of air is a constant it can be combined with
the
other constant in the ideal gas law when used for atmospheric calcs.


a minor nitpick on your minor nitpick is that the molecular weight of air is
not constant. It is affected by humidity.
density is better expressed as d = PM/RT
where d will be denity in units of mass/volume
(M is molecular weight), R the gas constant ,P and T press and Temp . For
us SI people R=8.31, P in Pa and T in Kelvin gives density in kg /m3 (
using M in kg/mole)Terry