Consider a phase diagram of Oxygen Nitrogen.
Now my question is : if a take a box containing air (80 % N2 - 20 % O2) at standard pressure and I start cooling it from room temperature to -196°C (BP of N2) what will be the composition of the liquid I obtain at -196°C ? What I understand is that at the dew point of air (-192°C) the composition of the mixture will be almost 50-50. Bt what will happen to this composition if I cool the box to -193°C, then -194°C... to -196°C? How will the composition of the liquid phase change ? and what will it be at -196°C ?