7440-59-7

IUPAC Name: Helium
Canonical SMILES: [He]
InChI: InChI=1S/He
Molecular Formula: He
Molecular Weight: 4 g/mol
EINECS: 231-168-5
Classification Code: Gases, diluent for
Melting Point: -272.2 °C(lit.)
Density: 0.1785（0 °C）
Vapor density: 0.14 (vs air)
Stability: Stable; extremely unreactive.
Enthalpy of Vaporization: 4.19 kJ/mol 
Boiling Point: -268.934 °C(lit.)
Critical point: 5.19 K, 0.227 MPa 
Vapour Pressure of Helium (CAS NO.7440-59-7): 1960000 mmHg at 25 °C

The first evidence of Helium (CAS NO.7440-59-7) was observed on August 18, 1868 as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun.
On March 26, 1895 British chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% rare earth elements) with mineral acids.
In 1907, Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei by allowing the particles to penetrate the thin glass wall of an evacuated tube, then creating a discharge in the tube to study the spectra of the new gas inside. In 1908, helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than one kelvin.Onnes' student Willem Hendrik Keesom was eventually able to solidify 1 cm3 of helium in 1926.
In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at temperatures near absolute zero, a phenomenon now called superfluidity. This phenomenon is related to Bose-Einstein condensation. In 1972, the same phenomenon was observed in helium-3, but at temperatures much closer to absolute zero, by American physicists Douglas D. Osheroff, David M. Lee, and Robert C. Richardson.

 Helium (CAS NO.7440-59-7) is used in cryogenics, in deep-sea breathing systems, to cool superconducting magnets, in helium dating, for inflating balloons, for providing lift in airships and as a protective gas for many industrial uses (such as arc welding and growing silicon wafers).

 Helium (CAS NO.7440-59-7) can be produced from natural gas. A typical plant removes the 2% helium from natural gas of up to 95 percent. The pipeline gas (at 3 to 4.5 MPa) is scrubbed, to remove water and condensable hydrocarbons and is then passed through a gas cleaner, which removes pipeline dust. From the cleaner, the gas goes to absorption towers to remove carbon dioxide (using monoethanolamine) and finally passes through a bauxite dryer. To obtain the helium, the purified gas enters coolers where the gas is chilled to -156 °C and then expanded into a separator-rectifier column. The natural gas is liquefied and separated and the crude-helium (75% helium, 25% nitrogen), passes through a heat exchanger counter to the incoming gas.
 The crude helium is purified by removing any trace amounts of hydrogen (using a reactor with a small amount of air, where the hydrogen is oxidized to water over a platinum catalyst) and the hydrogen-free gas is further purified utilizing a pressure-swing adsorption (PSA) process that removes all contaminants to a very low level, usually less than 10 ppm. The pressure-swing adsorption process does not remove neon but for most helium uses it is not considered a contaminant.

Reported in EPA TSCA Inventory.

A simple asphyxiant. A nonflammable gas. The safety issues for cryogenic helium are similar to those of liquid nitrogen; its extremely low temperatures can result in cold burns and the liquid to gas expansion ratio can cause explosions if no pressure-relief devices are installed. Containers of helium gas at 5 to 10 K should be handled as if they contain liquid helium due to the rapid and significant thermal expansion that occurs when helium gas at less than 10 K is warmed to room temperature.
Safety Statements: 9 
S9:Keep container in a well-ventilated place.
RIDADR: UN 1046 2.2
WGK Germany: 3
RTECS: MH6520000
F: 4.5-31

DOT Classification:  2.2; Label: Nonflammable Gas

  Helium (CAS NO.7440-59-7), its Synonyms are Atomic helium ; Helium-4 ; O-Helium ; UNII-206GF3GB41 ; p-Helium . It is colorless, odorless, noncombustible gas.