Argon, from argon meaning inactive, was discovered in 1894. It was found by analyzing atmospheric gases after removing oxygen and nitrogen. When all traces of carbon dioxide, dust, and moisture was also removed, there was enough gas that remained such that it was suspected that an additional gas was present. It is the most common of the noble gases. Like the other noble gases it is colourless, odourless and tasteless. It makes up 0.934% of the air and is released continuously by the decay of radioactive potassium in rocks (by electron-capture of 40K). The amounts of argon formed by radioactive decay in minerals serves as a method to determine the age of the specimen. Shown above is the glow discharge of argon.

Argon is used:

BCIT Chemistry Resource Center
http://nobel.scas.bcit.ca/resource/