  The article compares traditional coefficients of thermodynamic activity as a
parameter related to individual chemical species to newly introduced reduced
chaotic temperatures as system characteristics, both regarding their usage in
thermodynamic simulation of open chemical systems. Logical and mathematical
backgrounds of both approaches are discussed. It is shown that usage of reduced
chaotic temperatures and the Method of Chemical Dynamics to calculate chemical
and phase composition in open chemical systems is much less costly, easier to
perform and potentially leads to better precision.
