GB/T 40870-2021 Active

This document defines the commonly used quantities to describe the composition of a mixed gas:
——Mole fraction;
——Mass fraction;
——Volume fraction;
and
——Mole concentration;
——Mass concentration;
——Volume concentration.
For these composition quantities, this document provides methods for:
——Conversion between different quantities; and
——Conversion between different state conditions.
Conversion between different quantities refers to calculating the content value of another component under the same pressure and temperature conditions from the content value of a component in a mixed gas, all of which are the quantities listed above. Conversion between different states refers to calculating the content value of the same component in another state from the content value of a component in one state (i.e., temperature and pressure). By combining these two conversion methods, the composition of a mixed gas can be simultaneously converted between different component quantities and different state conditions.
This document only applies to homogeneous and stable mixed gases. Therefore, for any state conditions (pressure and temperature) involved, it is necessary to ensure that neither the mixed gas nor any specified analyte component undergoes condensation (see Appendix A).