
The Beginnings 11
where n is the number of moles, T the temperature in Kelvin, and R the so called gas
constant with a numerical value of 8.31 Joules/K.
1.2.2 Non-ideal gases
As already mentioned, in reality no gas is perfectly ideal and departures from the
gas laws discussed earlier are the rule rather than the exception. Many alternative
equations have been proposed, each with its positive as well as negative features.
Here are just a few of the most prominent ones.
van der Waals equation
P+
an
2
V
2
(V −nb)=nRT (1.15)
Clausius equation
P+
an
2
T(V + nc)
2
(V −nb)=nRT (1.16)
Dieterici equation
P(V −nb)=nRT e
−
an
VRT
(1.17)
Of these the van der Waals equation played ...