IV. Microscopic Reversibility and the Information Contained in the Composition Vector

In equilibrium systems, transitions at microscopic level are reversible. In this work the microscopic level is defined as the one corresponding to such a detailed description of the system composition that the observer, (1) for inability, cannot give, or (2) for his own decision, does not give. (These two situations, for practical purposes, are equivalent.) In order to clarify this point, theoretical aspects underlying the physical approach to chemical equilibrium problems are examined. On one hand, the reduction of the composition vector dimension carried out with no loss of the information needed to identify the system, results in the existence of element potentials. On the other hand, the element potentials independence on the state of the particles is compatible with dynamics at microscopic level and makes the Thermodynamics formalization consistent with this experimental fact. Therefore, as during reversible processes no composition information is generated by the system, when transforming composition variables, microscopic reversibility is the other side of the coin