The results of experiments on the investigation of the non-equilibrium behavior of a multicomponent hydrocarbon gas condensate mixture CH4–C3H8–C5H12–C7H16 in a free volume are presented in the article. The calculation of the thermodynamic properties of this mixture with a volume change (adiabatic compression–expansion) and sharp pressure drops in the container cell with a floating piston (recombiner) is presented. The phase equilibrium establishment time of 4-component mixture is determined. The mathematical model of the process in the context of the linearized problem of continuum mechanics using the phase diagram of the investigated mixture is developed. The reliability of the results obtained by calculation is confirmed by experimental studies in the cell of the recombiner.