2 also called pulmonary surfactant. one of certain lipoproteins that reduce the surface tension of pulmonary fluids, allowing the exchange of gases in the alveoli of the lungs and contributing to the elasticity of pulmonary tissue.
Helium is commercially recovered from natural gas deposits, mostly from Texas, Oklahoma and Kansas. Helium gas is used to inflate blimps, scientific balloons and party balloons. It is used as an inert shield for arc welding, to pressurize the fuel tanks of liquid fueled rockets and in supersonic windtunnels.
Liquid nitrogen is a diatomic liquid, which means that the diatomic character of the covalent N bonding in N 2 gas is retained after liquefaction. Liquid nitrogen is a cryogenic fluid that can cause rapid freezing on contact with living tissue.