Henry's law

This law states that the weighted amount of gas dissolved in a liquid at a constant temperature is directly proportional to the pressure of the gas above the liquid:

$$ c = \alpha \cdot P,$$

where c = concentration of the gas in the liquid, α = absorption coefficient (solubility of the gas depends on temperature, solubility decreases with increasing temperature), P = pressure.

Henry's law has relevance in respiratory physiology (Caisson disease) - it threatens people working at higher than atmospheric pressure who quickly go to normal pressure (miners, divers). The bubbles of nitrogen release into their blood that had previously got there by diffusion.