UNE-EN ISO 14912:2026

This document defines the following quantities commonly used to express the composition of gas

mixtures:

amount fraction,

mass fraction,

volume fraction,

and

amount concentration,

mass concentration,

volume concentration.

For these quantities of composition, this Document provides methods for

conversion between different quantities, and

conversion between different state conditions.

Conversion between different quantities means calculating the value of the content of a specified

component in terms of one of the quantities listed above from the value of the same content, at the same

pressure and temperature of the gas mixture, given in terms of another of these quantities. Conversion

between different state conditions means calculating the value of the content of a specified component,

in terms of one of the quantities listed above, under one set of state conditions from the value of the

same quantity under another set of state conditions, i.e. pressure and temperature, of the gas mixture.

Gas mixture composition can be converted simultaneously between different quantities of composition

and different state conditions by combination of the two types of conversion.

This document is applicable only to homogeneous and stable gas mixtures. Therefore any state

conditions (pressure and temperature) considered need to be well outside the condensation region

of the gas mixture. In addition, the use of volume concentrations requires that the component under

consideration is completely gaseous, and for the use of volume fractions even all components shall be

completely gaseous. Further restrictions of state conditions apply for approximations of compression

factors using virial coefficients (see Annex A).