Sir William Crookes, (June 17, 1832 – April 4, 1919) was an English chemist and physicist.

Sir William attended Royal College of Chemistry in London. Working on spectroscopy, in 1861 he discovered a previously unknown element with a bright green emission line in its spectrum. He named the element thallium, from the Greek thallos, a green shoot. Crookes also identified the first known sample of helium, in 1895.

He was the inventor of the Crookes radiometer, which today is made and sold as a novelty item. He also developed the Crookes tubes, investigating canal rays.

In his investigations of the conduction of electricity in low pressure gases, he discovered as the pressure was lowered, that the negative electrode appeared to emit rays (the so-called cathode rays, now known to be a stream of free electrons, and used in cathode ray display devices). He was one of the first scientists to investigate what are now called plasmas.

Trivia

• In 1910 He was appointed as a Member of the Order of Merit by King Edward VII.

External articles

• Hinshelwood, Cyril Norman, "William Crookes, A Victorian man of science". 1927.

External links

• The Cathode Ray Tube site