The Rüchardt experiment, invented by Eduard Rüchardt, is a famous experiment in thermodynamics, which determines the ratio of the molar heat capacities of a gas, i.e. the ratio of C p (heat capacity at constant pressure) and C V (heat capacity at constant volume) and is denoted by γ γ (gamma, for ideal gas) or κ κ (kappa, isentropic exponent, for real gas). It arises because the temperature of a gas changes as pressure changes.