As He called Helium, Helium, English symbols, colorless, tasteless, not flammable, the content is about 5.2 parts per million in the air.Chemically inert, condition not usually combined with other elements or compounds.On July 10, 1908, the Dutch physicist, nice liquefied helium gas for the first time.
Chinese name helium
English name Helium
Chemical formula He
The molecular weight of 4.003
The CAS login number 275-187-7
Melting point of 1.0 K (1.0 MPa)
Boiling point 4.3 K (4.3 MPa)
Water soluble poorly soluble in water
Dense degree of 0.1786 g/L (0 ° C and 0.1 MPa)
Outside view colorless
Safety description is flammable
Contain the amount of content in the air which is about 5.2 parts per million
Types of rare gas
Critical temperature 5.19 K
Critical pressure is 0.228 MPa
Evaporation heat 20.4 kJ/kg (boiling point)
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