Discovered : by Daniel Rutherford in 1772 Isolated in Edinburgh, UK Origin : The name is derived from the Greek ‘nitron genes’, meaning nitre forming : nitre is potassium nitrate, commonly known as saltpetre. Description : A colourless, odourless gas that makes up 78% of the air. Nitrogen is essential for life since it is part of DNA, but it is also needed for protein and many other components of the living cell. There is a so-called ‘nitrogen cycle’ in nature - that is, it is possible to trace its movements from the air to plants, to animals, to the soil where it can be recycled or washed into rivers, and where some microbes can turn it back into nitrogen gas and return it to the atmosphere. About 50 million tonnes of nitrogen are extracted every year, mainly for use as fertiliser, but also for making plastics, dyes and explosives. Image : Lightning is a major contributor to nitrogen fixation.