John Strutt (Lord Rayleigh), passing air and…

John Strutt (Lord Rayleigh), passing air and ammonia over red hot copper to produce nitrogen, isolates from the air a gas that he thinks is pure nitrogen, more than a century after Henry Cavendish's research on phlogisticated air.

The English physicist finds, however, that it is always about 0.5 percent more dense than nitrogen prepared chemically by liberating it from its compounds.

British chemist Sir William Ramsay, in collaboration with Rayleigh in 1894, isolates this gas, which proves to be a new element, named argon because of its chemical inertness.

Several unreactive gases are actually present; the first samples of argon also contain helium, neon, krypton, and xenon.

Ramsay obtains pure argon later by evaporating it from liquid air.