Applied Physics and Mathematics Annotation << Back ON THE INTERACTION OF GASES AND GASEOUS SOLUTIONS P.V. FEDOTOV Modern educational and scientific literature is based on the belief that any system consisting of two or more gases is a mechanical mixture of gases. Based on the analysis of the behavior of gases in the atmosphere, it is shown that such a statement is erroneous. A comparative analysis of the concepts of mixtures and solutions is carried out in order to clarify the criteria for differences. In particular, the analysis of the composition of air by altitude clearly indicates that nitrogen and oxygen in the atmosphere are not non-interacting gases that form a mechanical mixture, but a true gas solution. It is shown that the only criterion for differences between solutions and mixtures is solvation in solutions. When analyzing the thermodynamics of liquid solutions, the processes occurring during dissolution are clarified. Based on the analysis of air liquefaction technology and atmospheric gas separation technology, it is shown that liquid air is a true solution of liquid nitrogen and liquid oxygen, with unlimited mutual solubility. Based on a comparative analysis of liquid and gas solutions, an idea is put forward that the interaction of molecules in the gas phase repeats the interaction in the liquid phase, but in a weakened form. That is, if gases in a liquefied state form a liquid solution, then in the gas phase they also form a gas solution. Different methods for studying gas solutions are considered: liquefaction by cooling in the subcritical region, dissolution in supercritical liquids under pressure. Keywords: True solutions, mechanical mixtures, liquid solutions, solvation, thermodynamics of solutions, gas solutions, liquefaction of gases, supercritical liquids, fluids. DOI: 10.25791/pfim.06.2024.1314 Pp. 17-25.