A-to-Z Guide to Thermodynamics,
Heat & Mass Transfer, and Fluids Engineering
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One of the main empirical ideal-gas laws was established in 1662 by R. Boyle, and independently in 1676 by E. Mariotte. According to Boyle’s Law, at constant temperature (and low pressure) the volume V of a gas mass M is inversally proportional to its pressure p, i.e., pV = const. This law represents a description of the isothermal process of ideal gas.

The joint analysis of Boyle’s law and the empirical Charles’, Gay–Lussac’s and Avogadro’s laws can lead to the universal Equation of State of ideal gas — the Clapeyron (Clapeyron–Mendeleyev) equation. where is the molecular mass of gas, R is the universal gas constant (R = 8.314 J/mole K), and T is the absolute temperature.

This equation was subsequently rigorously substantiated by the molecular kinetic theory according to which p = nkT, where n is the number of molecules in unit volume, k is the Boltzmann constant (k = R/NA, NA = 6.022 1023 mole−1 is the Avogadro number, k = 1.381 10−23 J/K), from which follows the ideal gas equation of state and, accordingly, the expression for Boyle’s law.

As with the other ideal-gas laws, Boyle’s law is applicable at pressures far from critical, i.e., in that region of state, where one may neglect: a) the proper size of particles as compared to the interparticle distance; and b) the forces of interparticle interaction, where the energy of this interaction is considerably lower than the kinetic energy of particles.