Nitrogen, as the most abundant gas in the air, is inexhaustible and inexhaustible. It is colorless, odorless, transparent, subinert and does not support life. High purity nitrogen is often used as a protective gas in places where oxygen or air is isolated. The content of nitrogen (N2) in the air is 78.084% (the volume group of various gases in the air is divided into N2:78.084%, O2:20.9476%, Argon: 0.9364%, CO2: Other H2, CH4, N2O, O3, SO2, NO2, etc., but the content is very small), molecular weight is 28, boiling point: -195.8, condensation point: -210.