Liquid Air

Liquid Air is air that has been liquified.  Air is pressurized and then cooled. The cool air is allowed to escape through a small opening.  This reduces the temperature further. due to a phenomenon called the Joule Thomson effect.  The cold air is again compressed, cooled and allowed to escape through the opening.  This process is continued until the temperature drops further.  Droplets of liquid air are formed. 

Other gases such as liquid nitrogen and oxygen can be distilled from liquid air at specific temperatures.  For example, liquid nitrogen will separate from the mixture and evaporate at -195.79 deg.C.  The vaporized gas can be distilled separately to produce liquid nitrogen. 

Liquid air can also be used for cooling in many applications.