Argon is the most abundant and most used of the noble gases. Its chief uses are in metallurgy, where it provides an inert atmosphere in which hot metals can be worked. Because argon is so very unreactive, it prevents chemical reactions of the very hot metal being welded or forged. These are lamps constructed usually from clear, colorless glass tubes filled with a gas which emits light when an electric current passes through it. Oxygen is paramagnetic, that is, it is attracted to a magnet.
Liquid oxygen is pale blue.
In the steel industry, oxygen is passed through impure molten iron in a blast furnace to oxidize and remove impurities such as carbon, sulfur, phosphorus, and silicon. Oxygen is also used as the oxidant in torch cutting of steel. In this process, the steel is heated by an oxygen-acetylene flame, and a stream of hot oxygen is directed at the hot steel. The hot steel is oxidized by the hot oxygen and erodes away, severing the steel. The reaction of oxygen with another gas can lead to an explosion.