Thermodynamic treatment of kinetics of internal processes

In Chapter 1 we considered spontaneous processes inside a system when discussing the second law but later in that chapter we only considered equilibria. We shall now discuss the thermodynamic treatment of the kinetics of such processes. This field of thermodynamics is often called irreversible thermodynamics but the full term should rather be thermodynamics of irreversible processes. The word irreversible is often replaced by the word spontaneous. A process occurring inside a system may be caused by a change imposed upon the system by some external action, but it will here be regarded as a spontaneous result of the new conditions inside the system. All processes inside a system that actually occur will thus be regarded as spontaneous. It would really be unnecessary to use either of the terms irreversible and spontaneous processes if it were not for the need to distinguish them from the limiting case of a cyclic process, e.g. the Carnot cycle, when it is carried out in such a way that the internal processes it gives rise to produce a negligible amount of entropy. Since a cyclic process is controlled by actions from the outside and they could be performed in the reverse direction, it is possible to run the cycle in the reverse direction. All the internal processes it gives rise to will also reverse and if their entropy production is again negligible the two cases will be identical in the limit, except for the sign.