<P> Solid argon hydride (Ar (H)) has the same crystal structure as the MgZn Laves phase . It forms at pressures between 4.3 and 220 GPa, though Raman measurements suggest that the H molecules in Ar (H) dissociate above 175 GPa . </P> <P> Argon is produced industrially by the fractional distillation of liquid air in a cryogenic air separation unit; a process that separates liquid nitrogen, which boils at 77.3 K, from argon, which boils at 87.3 K, and liquid oxygen, which boils at 90.2 K . About 700,000 tonnes of argon are produced worldwide every year . </P> <P> Ar, the most abundant isotope of argon, is produced by the decay of K with a half - life of 1.25 × 10 years by electron capture or positron emission . Because of this, it is used in potassium--argon dating to determine the age of rocks . </P> <P> Argon has several desirable properties: </P>

Where does argon come from and how is it extracted