👉 Duffard's law, also known as the duffard equation, is a fundamental law in thermodynamics that relates the entropy of an ideal gas to its pressure and volume. It was first proposed by John F. Duffard (1876-1924) and has been extensively studied since then. The law states: dS/dP = -RT/P + nR/V Where: - dS/dP is the differential entropy of the gas -