Liquid air

Liquid air is a special form of air that has been cooled to very cold temperatures, turning it into a pale blue liquid. Because it is extremely cold, liquid air needs to be kept in special containers, like vacuum flasks, to protect it from warming up to room temperature. When liquid air absorbs heat, it quickly changes back into a gas.

This interesting substance is very useful in industry. It helps scientists and engineers separate air into its individual parts, such as nitrogen, oxygen, argon, and other inert gases, through a process known as air separation. These gases are important for many different jobs, from making steel to helping people breathe in hospitals. Liquid air’s ability to change temperature quickly makes it a valuable tool in many scientific and industrial jobs.

Properties

Liquid air is a very cold, pale blue liquid that forms when air is cooled to extremely low temperatures. It is much heavier than regular air, weighing about 870 kilograms per cubic meter. This weight can change a little depending on the mix of gases in the air.

Liquid air boils at around -194 degrees Celsius. This is colder than liquid nitrogen but warmer than liquid oxygen. Keeping liquid air at the right temperature can be difficult because the nitrogen in it often turns back into a gas first, leaving more oxygen behind. This can change the boiling point of what is left.

Preparation

Liquid air is made by cooling regular air until it turns into a liquid. Special machines are used to do this. Scientists first turned air into a liquid in 1883.

One common way to make liquid air today is called the Hampson–Linde cycle. This process presses air tightly and then lets it expand, which makes it very cold. This cold air can be used for experiments or, as some companies have tried, to power vehicles. In 2012, experts said liquid air might be a good way to store energy for future use.