# How can it be determined that a liquid is saturated with a gas?

How can it be determined if a liquid is saturated with a gas?

For example, if I am introducing carbon dioxide to water at 40 PSI at 35F in a sealed container, how would I know at what point the water is saturated with the gas?

• If the pressure of the gas above the liquid stays constant over time, the liquid is saturated with gas. – aventurin Sep 10 '17 at 17:58
• @aventurin That is true, but since the gas is being held at that pressure by a regulator, it is not useful. In other words, if we want to maintain a fixed pressure (which is 40 PSI in the example of the question), then there will be a regulator connected to the container which supplies the gas. The regulator ensures that the pressure remains at 40 PSI, so the pressure will not change. – Shaka Boom Sep 10 '17 at 18:20
• OK. The duration of the saturation process will e.g. depend on the area of the surface between liquid and gas, if the gas is injected into the liquid or not, if you shake the container, if you stir the liquid, and many other factors. Measuring the concentration of $\ce{CO2}$ in water would be a little more challenging than just waiting. Standard methods include titration or gas sensing electrodes. – aventurin Sep 10 '17 at 18:45
• You could monitor a spectroscopic peak as the gas is added to the solution. – jheindel Sep 12 '17 at 2:41