William Crookes

William Crookes 7 Kensington Park Gardens blue plaque

Thallium sample

Crookesite

Portrait of William Crookes as Hofmann's assistant

Portrait of William Crookes, age 24

Portrait of William Crookes, age 57

William Crookes (17 June 1832 – 4 April 1919) was an English chemist and physicist who made significant contributions to the fields of chemistry, physics, and spiritualism. He is best known for his work on cathode rays, leading to the discovery of the electron, and for his invention of the Crookes tube, an early experimental electrical discharge tube.

Early Life and Education

William Crookes was born in London, England, in 1832. He was educated at the Royal College of Chemistry, London, where he developed a strong interest in chemistry. Crookes began his career as a chemist, focusing on photographic chemistry and the study of thallium, a chemical element he discovered in 1861.

Scientific Contributions

Discovery of Thallium

In 1861, Crookes discovered the element thallium using flame spectroscopy, a technique that analyzes the spectral lines of elements. This discovery established his reputation as a chemist.

Cathode Rays and the Electron

Crookes' most notable contribution to physics was his work on cathode rays. In the 1870s, he invented the Crookes tube, a vacuum tube with electrodes at either end. When an electric current was passed through the tube, a stream of particles (later identified as electrons) was emitted from the cathode. This work laid the foundation for the eventual discovery of the electron by J.J. Thomson in 1897.

Radiometer

Crookes also invented the Crookes radiometer, a device that converts light radiation into rotary motion. The radiometer consists of a glass bulb containing a partial vacuum and four vanes mounted on a spindle. The vanes rotate when exposed to light, demonstrating the radiation pressure of light.

Spiritualism

In addition to his scientific work, Crookes was also involved in the study of spiritualism. He was a member of the Society for Psychical Research and conducted experiments with mediums, claiming to have observed physical phenomena produced by spiritualistic séances. His involvement in spiritualism was controversial and drew criticism from the scientific community.

Legacy

William Crookes' work had a profound impact on both chemistry and physics. His discovery of thallium expanded the periodic table, and his experiments with cathode rays were crucial in the development of atomic physics. The Crookes tube was a precursor to the development of X-ray technology and the television. Despite the controversy surrounding his interest in spiritualism, Crookes remains a significant figure in the history of science.

Death

William Crookes passed away on 4 April 1919 in London, England. His contributions to science are commemorated by the William Crookes Prize in spectroscopy and the Crookes Medal in radiometry.