UN1046 Helium High Purity Gases He Gas Controlled Atmospheres

UN1046 Helium High Purity Gases He Gas Controlled Atmospheres

Description:

Helium is a chemical element with symbol He and atomic number 2. It can be used for gas tungsten arac welding.

Helium is the second least reactive noble gas after neon, and thus the second least reactive of all elements. It is inert and monatomic in all standard conditions. Because of helium's relatively low molar mass, its thermal conductivity, specific heat, and sound speedin the gas phase are all greater than any other gas except hydrogen. For these reasons and the small size of helium monatomic molecules, heliumdiffuses through solids at a rate three times that of air and around 65% that of hydrogen.

Helium is the least water-soluble monatomic gas, and one of the least water-soluble of any gas, and helium's index of refraction is closer to unity than that of any other gas. Helium has a negative Joule-Thomson coefficient at normal ambient temperatures, meaning it heats up when allowed to freely expand. Only below its Joule-Thomson inversion temperature does it cool upon free expansion. Once precooled below this temperature, helium can be liquefied through expansion cooling.

Most extraterrestrial helium is found in a plasma state, with properties quite different from those of atomic helium. In a plasma, helium's electrons are not bound to its nucleus, resulting in very high electrical conductivity, even when the gas is only partially ionized. The charged particles are highly influenced by magnetic and electric fields. For example, in the solar wind together with ionized hydrogen, the particles interact with the Earth's magnetosphere, giving rise to Birkeland currents and the aurora.

Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements, as the alpha particles emitted by such decays consist of helium-4 nuclei. This radiogenichelium is trapped with natural gas in concentrations up to 7% by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation. Previously, terrestrial helium was thought to be a non-renewable resource because once released into the atmosphere, it readily escapes into space. However, recent studies suggest that helium is produced deep in the earth by radioactive decay, and that large untapped reserves may exist under the Rocky Mountains inNorth America and in natural gas reserves.

Specifications:

1. Physical properties

2. Typical technical data (COA)

3. Package

Applications: