formula_48 is defined as the elementary amount of mechanical work transferred by the operator to the ideal chain, and formula_49 is defined as the elementary amount of heat transferred by the solvent to the ideal chain. Now, if we assume that the transformation imposed by the operator on the system is quasistatic (i.e., infinitely slow), then the system's transformation will be time-reversible, and we can assume that during its passage from macro-state formula_2 to macro-state formula_51, the system passes through a series of thermodynamic equilibrium macro-states. This has two consequences: