If a gas is compressed adiabatically, i.e. without outflow of heat from the system, the temperature rises (due to the pressure increase) at a higher rate with respect to isothermal compression, where the performed work is dissipated as heat. The exponent, κ κ , with which the expansion of the gas can be calculated by the application of heat is called the isentropic – or adiabatic coefficient. Its value is determined by the Rüchardt experiment.