Gases Solved in Water - Diffusion Coefficients
Fick's first law states that a substance will flow from region with high concentration to a region of low concentration . Fick's law can be expressed as
J = -D*dφ/dx [1]
where
J = diffusion flux - the amount of substance that flows through an unit area per unit time [mass or mol /(m 2 s)]
D = diffusion coefficient [m 2 /s]
dφ = change in concentration of substance [mass or mol/m 3 ]
dx = change in length [m]
For simple one-dimensional transport, the diffusion coefficient describes the time–rate of change of concentration . The diffusion coefficient varies from substance to substance and with temperature.
See Water and Heavy Water - thermodynamic properties.
See also Water Boiling points at high pressure , Boiling points at vacuum pressure , Density, specific weight and thermal expansion coefficient , Dynamic and kinematic viscosity , Enthalpy and entropy , Heat of vaporization , Ionization Constant, pK w , of normal and heavy water , Melting points at high pressure , Saturation pressure , Specific gravity , Specific heat (heat capacity) and Specific volume for online calculatores, and similar figures and tables as shown below, as well as Air - Diffusion Coefficients of Gases in Excess of Air
Diffusion coefficients for some common gases in water:
(Gas–liquid diffusion coefficients are difficult to measure, and since the values below are from different sources and different measuring methods, there is some uncertainty about the values)
| Gas in water | Diffusion coefficient, D, [x10 -5 cm 2 /s ] at atmospheric pressure and given temperatures | ||||||
| 10 °C | 15 °C | 20 °C | 25 °C | 30 °C | 35 °C | ||
| Name | Formula | 50 °F | 59 °F | 68 °F | 77 °F | 86 °F | 95 °F |
| Acetylene | C2H2 | 1.43 | 1.59 | 1.78 | 1.99 | 2.23 | |
| Ammonia | NH3 | 1.30 | 1.50 | ||||
| Argon | Ar | 2.50 | |||||
| Bromomethane | CH3Br | 1.35 | |||||
| Carbon dioxide | CO2 | 1.26 | 1.45 | 1.67 | 1.91 | 2.17 | 2.47 |
| Chlorine | Cl2 | 1.13 | 1.50 | 1.89 | |||
| Chloromethane | CH3Cl | 1.40 | |||||
| Dichlorofluorumethane | CHCl2F | 1.80 | |||||
| Helium | He | 5.67 | 6.18 | 6.71 | 7.28 | 7.87 | 8.48 |
| Hydrogen | H2 | 3.62 | 4.08 | 4.58 | 5.11 | 5.69 | 6.31 |
| Hydrogen bromide | HBr | 3.15 | |||||
| Hydrogen chloride | HCl | 3.07 | |||||
| Hydrogen sulfide | H2S | 1.36 | |||||
| Krypton | Kr | 1.20 | 1.39 | 1.60 | 1.84 | 2.11 | 2.40 |
| Methane | CH4 | 1.24 | 1.43 | 1.62 | 1.84 | 2.08 | 2.35 |
| Neon | Ne | 2.93 | 3.27 | 3.64 | 4.03 | 4.45 | 4.89 |
| Nitrogen | N2 | 2.00 | |||||
| Nitrogen dioxide | NO2 | 1.23 | 1.40 | 1.59 | |||
| Nitrous oxide | N2O | 1.62 | 2.11 | 2.57 | |||
| Oxygen | O2 | 1.67 | 2.01 | 2.42 | |||
| Radon | Rn | 0.81 | 0.96 | 1.13 | 1.33 | 1.55 | 1.80 |
| Sulfur dioxide | SO2 | 1.62 | 1.83 | 2.07 | 2.32 | ||
| Xenon | Xe | 0.93 | 1.08 | 1.27 | 1.47 | 1.70 | 1.95 |
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