  The paper gives an account of a detailed investigation of the thermodynamic
branch as a path of the chemical system deviation from its isolated
thermodynamic equilibrium under an external impact. For a combination of direct
and reverse reactions in the same chemical system, full thermodynamic branch is
presented by an S-shaped curve, whose ends asymptotically achieve appropriate
initial states, which, in turn, are logistic ends of the opposite reactions.
The slope tangents of the steepest parts of the curves, the areas of the
maximum rate of the shift growth vs. the external thermodynamic force, occurred
to be directly proportional to the force and, simultaneously, linearly
proportional to the thermodynamic equivalent of chemical reaction, which is the
ratio between the amount in moles of any reaction participant, transformed in
an isolated system, along the reaction way from its initial state to
thermodynamic equilibrium, to its stoichiometric coefficient. The found
linearity is valid for arbitrary combination of the stoichiometric coefficients
in a reaction of compound synthesis from chemical elements like aA+bB=AaBb, and
confirms the exclusive role of the thermodynamic equivalent of transformation
as the chemical system characteristic of robustness and irreversibility.
Results of this work allow for quantitative evaluation of the chemical system
shift from thermodynamic equilibrium along thermodynamic branch and its rate
vs. the shifting force. Such an investigation became possible due to the
development of discrete thermodynamics of chemical equilibria.
