On the Air That We Breathe: Nitrogen and Oxygen

by Bob Dahl

Air.  We need air to breathe.  We feel the air when he swing our arms.

What is this air though? 

Technically speaking, the air around us is a mixture of 79.19 per cent nitrogen and 20.81 per cent oxygen. 

This mixture of the two gasses in the above proportions, principally form the atmosphere of the earth.

What are the two gasses for? 

The chief purpose of the nitrogen seems to be to dilute the oxygen which is constantly entering into combination with other elements or being set free from compounds, thus keeping up the general activity of nature. 

The animal world can be broadly described as consuming oxygen, while the vegetable world replaces the oxygen consumed. 

This doesn't mean though that plants never consume oxygen in their lives, or that they don't need it - when a seed is germinating, and at some other times, plant life consumes oxygen too. 

If we're scientific, and we burn a piece of coal, we can measure how many units of heat it will give out;  we can measure how much energy has been concerned, we can measure how much work with for example a steam engine this mutation of energy will accomplish, we can measure how much carbonic acid (not to be confused with carbolic acid) has been added to the atmosphere, and also we can measure how much oxygen has entered into combination with the carbon to form the carbonic acid. 

How to bring matters back to their unburned condition will involve at least as much energy, mutating in the inverse direction. 

Carbonic acid is the inorganic compound with the formula H2CO3 (equivalently OC(OH)2).  Carbonic acid is an intermediate step in the transport of CO2 out of the body via respiratory gas exchange. The hydration reaction of CO2 is generally very slow in the absence of a catalyst, but red blood cells contain carbonic anhydrase, which both increases the reaction rate and dissociates a hydrogen ion (H+) from the resulting carbonic acid, leaving bicarbonate (HCO3-) dissolved in the blood plasma. This catalysed reaction is reversed in the lungs, where it converts the bicarbonate back into CO2 and allows it to be expelled.

Carbonic acid basically will not split up back into oxygen and carbon, just like water would not naturally flow upwards onto a hill.  However, water does ascend to the tops of hills when the heat of the sun converts it into vapour.  Same way, carbonic acid also splits up into carbon and oxygen in contact with vegetable life acted on chemically by sunlight. 

Oxygen is more soluble in water than nitrogen, and hence the air dissolved in water contains about 10 per cent more oxygen than atmospheric air.  The oxygen therefore available for animals breathing by means of gills is somewhat less diluted with nitrogen, but much diluted with water.