For two substances of different boiling point (such as oxygen and nitrogen) compositing mixed solution, while after absorbing heat and partial evaporation, volatile composition nitrogen will evaporate more. Mixed steam releases heat and part of it condensates, while composition oxygen which is difficult to volatilize will condensate more. If you make saturated steam with higher temperature and saturated solution mixed, then steam gives off heat to saturated solution. After releasing heat, part of steam will condensate. Solution will absorb heat and part of it will evaporate. When partial steam’s condensation happens, due to oxygen condensates more, so the concentration of lower boiling point composition (nitrogen) in steam would be promoted.
During partial evaporation of solution, owing to nitrogen evaporates more, the concentration of higher boiling point composition (oxygen) will be promoted. If after partial evaporation and partial condensation are executed once, steam of higher concentration nitrogen and solution of higher concentration oxygen mix with solution and steam respectively with different temperature, then partial condensation and partial evaporation happen again, then the nitrogen concentration in steam and the oxygen concentration in solution will be promoted more procedures like this happen more times, then nitrogen concentration in steam will become higher and higher, at last we can achieve the purpose of separating oxygen and nitrogen.The whole press we call it distillation.
Generally speaking, the distillation is making use of different boiling point of two substances, and let the press of partially condensation of mixed steam and partially evaporation of mixed solution repeated, then finally we can achieve the purpose of separation.
