Jan Szargut (1923-), a Polish engineer noted for his advances in the theory of energy balances of chemical processes and for defining the reference states of chemical enthalpy and exergy. Enthalpy (H) is the is the sum of the internal energy of matter and the product of its volume multiplied by the pressure, while exergy is the maximum potential energy that can be extracted from a physical system when matter and energy are exchanged within a large reservoir in a reference state. Exergy distinguishes itself from energy because unlike energy, exergy can be destroyed and instead of remaining constant, exergy constantly decreases in physical processes. Szargut also made substantial contributions to the practical applications of exergy and energy analysis to chemical and metallurgical processes. He developed a method for calculating chemical exergy, and quantified the exergy analysis of common thermal processes and the economic and ecological application of exergy. He introduced the concept of thermo-ecological cost and thermo-ecological economy based upon the criterion of the minimization of the depletion of non-renewable natural resources. His monograph Exergy Analysis of Thermal, Chemical and Metallurgical Processes is the standard reference in the field.