The chemical system of monomolecular reactions among n species, first analysed in the classical paper by Wei and Prater (1962) was revisited. It was shown that using symmetry relationships, based on all the equilibrium constants and n(n - 1)/2 known dependences, all remaining kinetic dependences can be calculated. A new method of closing the mass balance for such a complex chemical system was developed, using only measurements of one or a few species, and based on symmetry relations. A new method of testing completeness of a kinetic description was proposed, using the properties of the trace sum of components, i.e., the sum of all concentration dependences, each of which is started from maximal initial concentration. (C) 2014 Elsevier Ltd. All rights reserved.