When first taught chemistry, one of the first things you learn from periodic table is that noble gases don't react. Well this is true… in part.
John William Strut (aka Lord Rayleigh) and William Ramsey discoved Argon (a noble gas) in 1894; Argon was the first noble gas to be isolated. Strut and Ramsey discovered the gas by the fractional distillation of liquid air. Fractional distillation is the process of letting liquid air slowly warm up; as the air warms different elements change from a liquid back to a gas. The portion of air that changes back to a gas at -185.86°C (-302.55°F) is Argon.