Nitrogen is prepared on a large scale by the fractional distillation of liquefied air. Air is composed of about 78% nitrogen and 21% oxygen, along with other gases. To obtain nitrogen, the air is liquefied by compressing and cooling it to a very low temperature. This liquefied air is then separated into its components by fractional distillation, a process in which the different gases are separated based on their boiling points. Since nitrogen has a lower boiling point than oxygen, it boils off first and can be collected. This process is used to obtain large amounts of nitrogen for industrial and commercial purposes.