Air

Air. Ordinary and Liquid air.

I want to begin with liquid air is a mixture of the liquefied gases. It is a milky liquid owing to the presence of solid carbon dioxide and ice. If these solids were removed by filtering, the filtrate would have a pale blue tint.

Ordinary air contains nearly constant proportions of three elementary substances, such as nitrogen — 75.4 per cent, oxygen — 23.2 per cent and argon — 1.2 per cent by weight.

Applications

Firstly, Liquid air due to its extremely low temperature produces remarkable physical changes.

If a tin or iron vessel were cooled by liquid air, it would become so brittle that it could be crushed with the fingers.

Secondly, Mercury freezes so hard in liquid air that it could be used as a hammer. It could be hardly crushed.

If the liquid air were in a tea kettle standing on a block oi ice, the liquid air would boil vigorously. If the kettle of liquid air were placed over a lighted Bunsen burner, frost and ice would collect on the bottom of the kettle.

Thirdly, Ordinary liquid air is from one half to one fifth liquid oxygen, and therefore it can support combustion.

A red hot rod of steel would have burned brilliantly if it had been placed in the liquid air.

Lately numerous applications of liquid air have been pro­posed and have been used in all branches of life. For example, it can be used to remove diseased flesh from the wounds. It can be widely used as commercial source of oxygen and nitro­gen. Liquid air can be readily manufactured in large quanti­ties at a comparatively low cost, that is why liquid air is made use of both in industry and in everyday life.

As for ordinary liquids, The relative proportion of water vapour in the air could be stated in terms of relative humidity, i. e. the ratio between the concentration of water vapour in the air and the concentration required for equilibrium at the same temperature.

If the relative humidity were low, evaporation would oссur rapidly. If the relative humidity were high, evapora­tion would occur slowly as the air is nearly saturated.

In conclusion, I want to say that every types of liquids is unique and important.