Colorless, odorless, flammable gas. Relative density d2 1.0493 (air-1) or density 1.3562g/L; Basic (solution) o.446; mp – 172℃； bp-88℃； Critical temperature 32.2 ℃, critical pressure 4883 9kPa, critical density 203 Okg/m3。 Triple point -183 27℃(0.lOIMPa)； Latent heat of evaporation 489.41kj/kg; At the triple point, the latent heat of melting is 95. At saturation pressure, the relative density of the liquid is 0 3771 (15.6 ℃). The flammability limit in air is 3.0% to 12.4% by volume, with a flash point of -135 ℃.
It is widely used as a standard gas, calibration gas, etching gas, online instrument standard gas, catalyst evaluation gas, preparation of certain special mixed gases, and for the study of certain mechanisms in industrial sectors such as chemical engineering, metallurgy, electronics, petroleum, scientific research, aviation, and atomic energy.