The equilibrium or saturation concentration of gas dissolved in a liquid is a function of the type of gas and the partial pressure of the gas adjacent to the liquid. The relationship between the partial pressure of the gas in the atmosphere above the liquid and the concentration of the gas in the liquid is given by Henry s law:

where<i class="emphasis">P</i><sub<i class="emphasis">g</i></sub> = partial pressure of gas, atm<i class="emphasis">H</i> = Henry s law constant<i class="emphasis">x</i><sub<i class="emphasis">g</i></sub> = equilibrium mole fraction of dissolved gas= mol gas (<i class="emphasis">n</i><sub<i class="emphasis">g</i></sub>)/[mol gas(<i class="emphasis">n</i><sub<i class="emphasis">g</i></sub>) + mol water(<i class="emphasis">n</i><sub<i class="emphasis">w</i></sub>)]

Henry s law constant is a function of the type, temperature, and constituents of the liquid. Values of H for various gases are listed in Table E.3. Use of the data in Table E.3 is illustrated in the following example.