Boyle's law (also known as the Boyle Mariotte law) is one of the gas laws, and relates the volume and pressure of an ideal gas held at a constant temperature.

The law, expressed in symbols, is:

PV = k

where

V is the volume of gas measured in cubic metres or litres

P is its pressure measured in pascals

k is a constant

To maintain the constant during an increase in pressure of a gas, at fixed temperature, requires that the volume decrease. Conversely, reducing the pressure of the gas increases the volume.

The exact value of the constant need not be known to make use of the law in comparison between two volumes of the same amount of gas at equal temperature:

P₁V₁ = P₂V₂

Together with the Law of Charles and Gay-Lussac and Graham's law, Boyle's law forms gas laws, which describes the behaviour of an ideal gas. The three gas laws can be generalized by the universal gas equation.

Boyle's Law is named after the Irish natural philosopher Robert Boyle (1627-1691). Edme Mariotte (1620-1684) was a French physicist who discovered the same law independently of Boyle at roughly the same time, so this law is often known as Mariotte's or Mariotte Boyle law.

This law is used in basic chemistry.

See also

• Scientific laws named after people