For example, if the gas has a composition of 80% N and 20% O and is cooled below 79 K, the liquid formed will have a composition of 53% N and 47% O (see Ref. 14, p. 14.).
In our model, a fixed fraction of the number of molecules that collide with the cold wall condense; for a balloon filled with air, a variable fraction of molecules (strongly dependent on the particular mixture of gases) that collide with the cold wall condense, and this time dependent fraction modifies the volume time dependence.