Mixing ratio

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In chemistry and physics, the dimensionless mixing ratio is the abundance of one component of a mixture relative to that of all other components. The term can refer either to mole ratio or mass ratio.[1]

In atmospheric chemistry and meteorology[edit]

Mole ratio[edit]

In atmospheric chemistry, mixing ratio usually refers to the mole ratio ri, which is defined as the amount of a constituent ni divided by the total amount of all other constituents in a mixture:

The mole ratio is also called amount ratio.[2] If ni is much smaller than ntot (which is the case for atmospheric trace constituents), the mole ratio is almost identical to the mole fraction.

Mass ratio[edit]

In meteorology, mixing ratio usually refers to the mass ratio ζi, which is defined as the mass of a constituent mi divided by the total mass of all other constituents in a mixture:

The mass ratio of water vapor in air can be used to describe humidity.

Mixtures/solutions mixing ratio[edit]

Two binary solutions of different compositions can be mixed with various mixing ratios by masses, moles, or volumes.

The mass fraction of the resulting solution from mixing solutions with mass fractions w1 and w1 is given by:

or, by substituting the densities and considering equal volumes of different concentrations

The formula can be extended to more than 2 solutions to be mixed giving:


  1. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "mixing ratio".
  2. ^ "Pure and Applied Chemistry, 2008, Volume 80, No. 2, pp. 233-276". Iupac.org. 2016-06-14. Retrieved 2016-06-30.