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Diffusion Coefficients of Gases in Water
Fick's First Law
A substance dissolved in a liquid flows from regions of high concentration to regions of low concentration. Fick's first law quantifies this flux:
J = −D dφ/dx
where:
- J — diffusion flux: amount of substance flowing through a unit area per unit time (kg/(m²·s) or mol/(m²·s))
- D — diffusion coefficient (m²/s)
- dφ — change in concentration (kg/m³ or mol/m³)
- dx — change in length (m)
For simple one-dimensional transport, D describes the time-rate of change of concentration. It varies from substance to substance and increases with temperature.
Note: Gas–liquid diffusion coefficients are difficult to measure. Values below are compiled from different sources and measuring methods, so some uncertainty in the values should be expected.