Henry's Law

When a gas is in contact with the surface of a liquid, the amount of the gas which will go into solution is proportional to the partial pressure of that gas. A simple rationale for Henry's law is that if the partial pressure of a gas is twice as high, then on the average twice as many molecules will hit the liquid surface in a given time interval, and on the average twice as many will be captured and go into solution. For a gas mixture, Henry's law helps to predict the amount of each gas which will go into solution, but different gases have different solubilities and this also affects the rate. The constant of proportionality in Henry's law must take this into account. For example, in the gas exchange processes in respiration, the solubility of carbon dioxide is about 22 times that of oxygen when they are in contact with the plasma of the human body.