Gas laws 1662 Robert Boyle studied the relationship between volume and pressure of a gas of fixed amount at constant temperature. He observed that volume of a given mass of a gas is inversely proportional to its pressure at a constant temperature. Boyle's law, published in 1662, states that, at constant temperature, the product of the pressure and volume of a given mass of an ideal gas in a closed system is always constant. It can be verified experimentally using a pressure gauge and a variable volume container. It can also be derived from the kinetic theory of gases: if a container,
Molar volume an ideal gas: Hence, for a given temperature and pressure, the molar volume is the same for all ideal gases and is known to the same precision as the gas constant: "R" = 0.082 057 338(47) L atm K mol, that is a relative standard uncertainty of 5.7×10, according to the 2014 CODATA recommended value. The molar volume of an ideal gas at 100 kPa (1 bar) is The molar volume of an ideal gas at 1 atmosphere of pressure is For crystalline solids, the molar volume can be measured by X-ray crystallography. The unit cell volume ("V") may be