The phenomenon of "Conservatively Perturbed Equilibrium" (CPE) in chemical kinetics is distinguished using a sequence of first-order reactions (linear mechanism) and non-linear mechanisms as well. In this phenomenon, some, not all initial concentrations of the closed chemical system are replaced by the corresponding equilibrium concentrations at the same total amount of each chemical element. Properties of CPE-phenomenon are described: 1. For the substance which initial concentration is taken as the equilibrium one, the concentration extremum in a way to the equilibrium is unavoidable. 2. This extremum can be a momentary partial equilibrium for some steps of the chemical mechanism. 3. Time of occurrence of this extremum is independent of the perturbation. Properties 1 and 2 are general properties. Property 3 is specific for the linear mechanism studied. (C) 2018 Elsevier Ltd. All rights reserved.