In chemistry and physics, Dalton's law (also called Dalton's law of partial pressures) states that the total pressure exerted by a gaseousmixture is equal to the sum of the partial pressures of each individual component in a gas mixture. This empirical law was observed by John Dalton in 1801 and is related to the ideal gas laws.

Mathematically, the pressure of a mixture of gases can be defined as the summation

       or      

where  represent the partial pressure of each component.

It is assumed that the gases do not react with each other.

where  the mole fraction of the i-th component in the total mixture of m components .