Argon

Name:
Argon
Detailed information:
(Ar). A nonmetallic element of atomic number 18, in the noble gas group of the Periodic System. Aw 39.948. Present in atmosphere to 0.94% by volume.

Properties:

Colorless monatomic gas; odorless; tasteless. It is not known to combine chemically with any element, but forms a stable clathrate with β-hydroquinone. Fp −189.3C, bp −185.8C,d 1.38 (air = 1), sp vol 9.7 cu ft/lb (21.1C @ 1 atm). Slightly soluble in water. Noncombustible; an asphyxiant gas.

Derivation:

(1) By fractional distillation of liquid air. (2) By the treatment of atmospheric nitrogen with metals such as magnesium and calcium to form nitrides. (3) Recovery from natural gasoxidation bottoms-steam in ammonia plant. (4) Originally formed by radioactive decay of 40K.

Method of purification:

(1) Highly purified argon is obtained by passing the gas through a bed of titanium at 850C. (2) Synthetic zeolite molecular sieves separate oxygen from argon to givehigh purity gas.

Grade:

Technical, highest purity (99.995%).

Use:

Inert-gas shield in arc welding, furnace brazing, plasma jet torches (with hydrogen), electric and specialized light bulbs (neon, fluorescent, sodium vapor, etc.; titanium and zirconiumrefining; flushing molten metals (steel) to remove dissolved gases; in Geiger-counter tubes; lasers; inert gas or atmosphere in miscible applications; decarburization of stainless steel (AODprocess).