Sir William Crookes
(born June 17, 1832,
London
, Eng.?died April 4, 1919, London) was a British chemist and physicist noted for his discovery of the element thallium and for his cathode-ray studies, fundamental in the development of
atomic physics
.
After studying at the Royal College of Chemistry, London, Crookes became superintendent of the meteorological department at Radcliffe Observatory,
Oxford
, in 1854, and the following year gained a post at the College of Science in Chester, Cheshire. Having
inherited
a large fortune from his father, he devoted himself from 1856 entirely to scientific work of various kinds at his private laboratory in London. His researches on electrical discharges through a rarefied gas led him to observe the dark space around the cathode, now called the
Crookes dark space. He demonstrated that cathode rays travel in straight lines and produce phosphorescence and heat when they strike certain materials. He invented many devices to study the behaviour of cathode rays, but his theory of radiant matter, or a fourth state of matter, proved incorrect in many respects.
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Faces of Science
With the introduction of spectrum analysis by R.W. Bunsen and G.R. Kirchhoff, Crookes applied the new technique to the study of
selenium
compounds
. In 1861 he discovered
thallium
in some seleniferous deposits. He continued work on that new element, isolated it, studied its properties, and in 1873 determined its
atomic weight
.
During his studies of thallium, Crookes discovered the principle of the
Crookes radiometer
, a device that converts light
radiation
into rotary motion. The principle of this radiometer has found numerous applications in the development of sensitive measuring instruments. Crookes was knighted in 1897.