How does a vacuum remove dissolved gases from oils and other materials?

In the context of vacuum technology, the removal of dissolved gases from liquids—such as oils or molten steel—relies on the relationship between gas solubility and pressure, often described by Henry’s law.

According to Henry’s law, the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas above the liquid’s surface. By exposing a material to a vacuum, the pressure of the surrounding gas is significantly reduced. This drop in pressure disrupts the equilibrium, causing the dissolved gases to escape the liquid phase and transition into the gas phase, where they can be removed by vacuum pumps or steam ejectors.123

In industrial applications like steelmaking, this process is used to lower levels of dissolved hydrogen and nitrogen. It also facilitates chemical reactions, such as the removal of carbon and oxygen by forming carbon monoxide, which then exits the melt under the reduced pressure of the vacuum environment. The efficiency of this removal depends on factors such as the duration of the treatment and the ability of gas atoms to migrate through the liquid to the surface.2