👉 Hartmann's law, also known as the Hartmann-Edwards equation, is a fundamental conservation law in thermodynamics that describes the relationship between temperature and pressure in a closed system. This law states that for an ideal gas at constant volume (V = const), the total entropy S of the system increases with both temperature T and pressure P, given by: \[ \frac{dS}{dT} + \frac{P}{T}\frac{dP}{dt} =