Crookes, Sir William (1832-1919), was a British chemist and physicist. Crookes discovered the chemical element thallium and determined its relative atomic mass (atomic weight). He also developed several devices that were widely used in scientific research for many years.
During the 1870’s, Crookes constructed a vacuum tube for studying a form of radiation that came to be called cathode rays. This device, which became known as the Crookes tube, contributed to the development of the modern cathode-ray tube. For many years, cathode-ray tubes were the primary component of television displays and computer monitors. Crookes was also the inventor of the radiometer, a device that measures the intensity of radiant energy.
Crookes was born on June 17, 1832, in London and graduated from the Royal College of Chemistry in 1851. In 1859, he founded the journal Chemical News. He was knighted in 1897. He died on April 4, 1919.
See also Crookes tube; Vacuum tube.
