flow rate

in flame emission and absorption spectrometry
https://doi.org/10.1351/goldbook.F02440
The volume rate of one component, X (e.g. air, O2 ), of the unburnt gas mixture (such as C2H2, O2, etc.) in the burner tip. Ambient temperature and pressure must be stated.
Source:
PAC, 1986, 58, 1737. 'Quantities and units in clinical chemistry: Nebulizer and flame properties in flame emission and absorption spectrometry (Recommendations 1986)' on page 1742 (https://doi.org/10.1351/pac198658121737)