How this calculator works
Dalton mode multiplies gas-phase mole fraction by total absolute pressure. Ideal-gas modes use the component amount and whole mixture volume. Henry-law modes describe a gas dissolved in a liquid at equilibrium, with a user-supplied constant for the actual gas, solvent and temperature. Hcp multiplies pressure to give concentration; Hpx multiplies liquid mole fraction to give pressure. These conventions are not interchangeable.
Formula
p_i = x_i p_total = n_i RT/V. Henry forms: c_liquid = Hcp p_i; p_i = Hpx x_liquid.
Worked example
At total pressure 100 kPa and gas fraction 0.2, partial pressure is 20 kPa. With Hcp = 1.3 x 10^-5 mol m^-3 Pa^-1, that pressure gives 0.26 mol/m3 dissolved gas.
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Frequently asked questions
Which Henry constant should I enter?
Use the specified convention and SI units from a source for your gas, solvent and temperature. The example default is illustrative of oxygen in water near 25 C.
Can I use gauge pressure?
Use absolute pressures for gas laws and phase-equilibrium relations.
Are gas and liquid mole fractions equal?
Generally no. The Henry modes use the dissolved liquid fraction; Dalton uses the gas fraction.