# Gas constants

From Glossary of Meteorology

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## gas constant

The constant factor in the equation of state for ideal gases.

The universal gas constant is The gas constant for a particular gas is where where The gas constant for water vapor is For moist air, the variable percentage of water vapor is taken into account by retaining the gas constant for dry air while using the virtual temperature in place of the temperature.

*m*is the molecular weight of the gas. For a mixture, the "molecular weight" is a weighted mean of the molecular weights of the components:*m*_{1}, · · ·,*m*_{n}are the molecular weights of the*n*gases, and*f*_{1}, · · ·,*f*_{n}are their masses relative to the total mass of the mixture. The gas constant for dry air is

R= 2.870 × 10_{d}^{2}J/(kg*K)

R= 4.615 × 10_{d}^{2}J kg^{-1}K^{-1}

*See also*Boltzmann's constant.