Mixing ratio

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In chemistry and physics, the dimensionless mixing ratio is defined as 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]

Mole ratio[edit]

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

r_i = \frac{n_i}{n_{tot}-n_i}

The mole ratio is also called amount ratio.[2]

If n_i is much smaller than n_{tot} (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 \zeta_i, which is defined as the mass of a constituent m_i divided by the total mass of all other constituents in a mixture:

\zeta_i = \frac{m_i}{m_{tot}-m_i}

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

References[edit]

  1. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "mixing ratio".
  2. ^ http://www.iupac.org/publications/pac/80/2/0233/