HENRY'S LAW: The amount of any gas that will dissolve in a liquid, at a given temperature, is a function of the partial pressure of that gas in contact with the liquid, and the solubility coefficient of the gas in the particular liquid.

Simply stated for divers: As a diver descends, more gas will dissolve in the body tissues. Upon ascent the dissolved gas must be released. When air is breathed under pressure, the inert nitrogen diffuses into the various body tissues with the amount of uptake varying for different tissues. The amount of nitrogen uptake increases as the partial pressure increases, or as the diver goes deeper. After the dive, and the diver ascends the process is reversed. Nitrogen will come out of the tissues it was forced into, and if this release is uncontrolled, bubbles of nitrogen gas can form in the tissues and blood, causing decompression sickness.

The pressure of a gas is the measurement of its molecular activity. When a gas is heated, the molecular activity seeds up thus there is a corresponding increase in pressure. When the gas is cooled, the molecular activity slows, and pressure decreases. The physicist who discovered this was named Charles..

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