William Crookes
Early Life and Education
William Crookes was born on June 17, 1832, in London, England. He was the eldest of sixteen children in a prosperous tailor's family. Crookes attended the Royal College of Chemistry, where he studied under the renowned chemist August Wilhelm von Hofmann. His early education laid a strong foundation in chemical sciences, which would later influence his diverse scientific pursuits.
Career and Contributions
Discovery of Thallium
In 1861, Crookes discovered the element thallium while investigating the residues of sulfuric acid production. He identified the new element through its bright green spectral line, a method known as spectroscopy, which was relatively novel at the time. This discovery marked a significant milestone in analytical chemistry and showcased Crookes' innovative approach to scientific research.
Cathode Rays and the Crookes Tube
Crookes is perhaps best known for his work on cathode rays. In the late 1870s, he developed the Crookes tube, an early experimental electrical discharge tube with partial vacuum. This device was crucial in the study of cathode rays and laid the groundwork for the development of X-rays and the electron. His experiments demonstrated that cathode rays travel in straight lines and can cause fluorescence when they strike certain materials.
Radiometer
In 1873, Crookes invented the radiometer, also known as the light mill. This device consists of an airtight glass bulb containing a partial vacuum and a rotor with several (usually four) vanes, which are black on one side and white on the other. When exposed to light, the vanes rotate, with the black sides retreating from the light source. This invention was initially thought to demonstrate the pressure of light, but it was later understood to be due to thermal transpiration.
Spiritualism and Psychical Research
Crookes was also deeply involved in spiritualism and psychical research. He conducted several experiments with mediums, including Florence Cook and Daniel Dunglas Home, and claimed to have observed genuine paranormal phenomena. His involvement in this field was controversial and drew criticism from some of his contemporaries, who questioned the scientific rigor of his investigations.
Later Life and Honors
In his later years, Crookes continued to contribute to various scientific fields. He was knighted in 1897 for his services to science and became Sir William Crookes. He served as president of the Royal Society from 1913 to 1915 and was awarded numerous honors, including the Copley Medal and the Davy Medal.
Legacy
William Crookes left a lasting legacy in the scientific community. His pioneering work in spectroscopy, cathode rays, and the invention of the radiometer significantly advanced the understanding of physical and chemical phenomena. Despite the controversy surrounding his involvement in spiritualism, his contributions to science remain highly regarded.