Wegscheider's condition and passivity of open chemical reaction systems 1

The second law imposes a number of constraints on the set of feasible reaction rate coefficients that a chemical network can accept, known in the literature on CRNT (Chemical Reaction Network Theory) as Wegscheider's condition. One main consequence is that any closed chemical reaction system operating at isothermal conditions, if compatible with thermodynamics, must be complex balanced, otherwise the Wegscheider's condition is violated. In this contribution we make use of this observation to conclude passivity of open reaction systems with respect to a Gibbs energy function, what in turn allows us to point on mass and energy exchanges with the environment, as the main causes that make chemical reactors unstable. As it will be discussed, control of open reaction systems can take advantage of this fact to design input-output stabilizing feed-back controllers.