BoyleMariotte

The Boyle–Mariotte law, also known as Boyle's law or Mariotte's law, describes how the pressure of a given amount of gas at constant temperature is inversely proportional to its volume. The law states that for a fixed amount of gas, P is proportional to 1/V, so that PV = constant. In a closed system with n moles of ideal gas and at constant temperature T, P V = n R T, so if T and n are constant, P1V1 = P2V2 for any two states.

The law holds as an empirical relationship for gases under isothermal conditions and is a special case of the ideal gas law. It is most accurate for low pressures where intermolecular forces and the finite size of molecules are negligible; deviations occur as pressures rise and real-gas effects become significant.

Historically, the relationship was discovered by Robert Boyle in the 17th century through experiments on the elasticity of air. Independently, Edme Mariotte described the same relationship in his work in France around 1676. The term Boyle–Mariotte law is common in many European and non-English texts; in English, it is frequently referred to as Boyle's law or Mariotte's law.

Applications of the Boyle–Mariotte law appear in diverse areas such as respiration and inhalation, the functioning of syringes, and the analysis of piston-based engines and other devices involving gas compression. Limitations include deviations from ideal behavior at high pressures, as well as processes that involve temperature changes, phase transitions, or non-equilibrium conditions.