Patients who are very ill or have breathing problems are given extra oxygen so that their lungs do not have to work so hard, and they recover quicker.
Oxygen can also be used to cut and weld steel using a kind of torch called an oxyacetylene torch. In this type of torch, the gas acetylene burns in pure oxygen to produce a temperature of more than 8600 degrees F (3000 degrees C). This melts the steel and leaves a cut. Oxyacetylene torches are also used to weld. Two edges of steel melt in the torch flame and join up as they cool.
When iron and steel are left in wet weather, they are rapidly covered with an orange-brown deposit called rust. This is iron oxide, the result of a chemical reaction between iron, oxygen, and water.
Another chemical reaction is burning. There are three things that are needed to make a fire: heat, oxygen, and fuel. If a fire does not have all three of these things, the fire can't start or will rapidly go out. This is the reason that a campfire covered with sand or stones goes out. The sand or stones keep out oxygen.
Oxygen has two natural allotropes. O2 is the common form in the atmosphere etc. Ozone O3, is a byproduct of pollutants and reactions in the upper atmosphere between O2 and cosmic rays. Oxygen has an oxidation number of 0 in O2 and -3 in ozone.
In 1774, English chemist Joseph Priestley announced he had discovered oxygen, never realizing that it had been discovered by Swedish chemist Carl Scheele several years earlier. These two proved that air was not one element. However, they did not realize what they had discovered. In 1775, French chemist Antoine Lavoisier proved what oxygen is.