An ideal or perfect gas is one which obeys the equation of state, PV = nRT, where T is the absolute temperature in Kelvin degrees (equal to the temperature in Celsius degrees plus 273 degrees) and R is the universal gas constant (equal to 0.08 when the volume V is in liters, the pressure P is in atmospheres, and n is the number of moles of the gas present; or equivalently, 8.3 joules per degree mole.)

This equation resulted from the examination of the behavior of air by Robert Boyle, Jacques Charles, and Joseph- Louis Gay-Lussac. Based on experimental measurements, Boyle showed that the product of the pressure and the volume of a sample of air, at constant temperature, is always equal to the same value. In other words, when the pressure placed on the sample is doubled, the volume is reduced to half its initial value. The work of...