It is difficult to make NO2 without making NO, and my experience is that the NO dissolves readily in liquid NO2, that is, at temperatures well above
the boiling point of NO but below that of NO2. Of course it is not just dissolving in it, it is reacting to form N2O3, which gives the blue color.
But as you raise the temperature toward the boiling point of NO2, the NO comes off.
It is difficult to eliminate all the NO without mixing with oxygen in the gas phase and giving it time to react. You have to do this before you cool
it, if you want to get pure liquid NO2. |