FRONTIERS ARTICLEMass action in ionic solutions

The law of mass action describes reactants as simple ideal fluids of concentrations of uncharged noninteracting particles. Ionic solutions contain interacting charged particles and are not ideal. Interactions of reactants can then be mistaken for complexities in chemical reactions or enzymatic catalysts. The variational theory of complex fluids describes flowing mixtures like biological solutions. When a component is added, the theory derives-by mathematics alone-a new set of differential equations that automatically captures all interactions. A variational theory of ionic solutions (as complex fluids) provides computable description of ions in solutions and proteins. Numerical inefficiencies have delayed experimental verification.

95Research highlights► Ionic solutions are rarely ideal. ► Law of Mass Action assumes ideal solutions. ► Artifactual states can arise when mass action is inappropriate. ► Enzymes can appear to have multiple states, if ionic reactants are assumed to be ideal. ► Energy Variational Analysis deals with nonideal interacting and flowing solutions