Abstract
Isothermal diffusion and convective mixing in a ternary He–Ar–N2 mixture at varying pressures and initial compositions were examined experimentally by means of the two-flask method. The study was conducted under strictly controlled laboratory conditions to ensure precise, comparable, and reproducible results across all experiments. It was found that when the density decreases with height, the mechanical equilibrium of the mixture can be disturbed, causing gravitational flows and partial convection within the system. Anomalous transfer of the component with the greatest molecular mass was detected at particular pressures and starting compositions, pointing to the influence of supplementary convective processes beyond ordinary diffusion. When the experimental results were plotted in the phase space of the three variables — pressure, initial com position, and diffused component concentration — a pronounced wave-like iso-concentration surface emerged. This surface appeared in regions corresponding to well-developed convective flows. Its formation correlated with the highest intensity of partial component mixing, highlighting the combined influence of pressure, composition, and gravitational effects on the mixture’s dynamic equilibrium. These findings provide insight into the interplay between diffusion and convection in multicomponent gas systems, revealing condi tions under which gravitationally induced flows significantly alter component transport and overall mixture behavior.