BOYLE'S LAW

also called Mariotte's Law, a relation concerning the compression and expansion of a gas at constant temperature. This empirical relation, formulated by the physicist Robert Boyle in 1662, states that the pressure (p) of a given quantity of gas varies inversely as its volume (v) at constant temperature; i.e., in equation form, pv = k, a constant. The relationship was also discovered by the French physicist Edme Mariotte (1676). The law can be derived from the kinetic theory of gases assuming a perfect (ideal) gas (see perfect gas). Real gases obey Boyle's law at sufficiently low pressures, although the product pv generally decreases slightly at higher pressures.