# Equation of state

From Glossary of Meteorology

## equation of state

(Also known, for an ideal gas, as the Charles–Gay–Lussac law, or Charles law, or Gay–Lussac's law.) An equation relating temperature, pressure, and volume of a system in thermodynamic equilibrium.

The equation of state for an ideal gas of where where α is the specific volume and

*N*molecules in a volume*V*is*p*is pressure,*T*is absolute temperature, and*k*is Boltzmann's constant. After division by the mass of the volume, this may also be written as*R*is an individual gas constant. For a mixture of gases, a similar equation may be written with the aid of Dalton's law, where*R*becomes a weighted average of the individual gas constants.