It is notable that several other scientists had devised tubes similar to those used by Crookes in the years before he embarked on his studies in the area. His experiments, however, helped reveal important new information about the nature of the mysterious rays. At the time of Crookes’s initial studies, however, the fluorescent light was poorly understood, being attributed to enigmatic rays, which were called cathode rays because they appeared to be emitted by the negative electrode. It is now known that the glow is due to the interaction of electrons, which travel from the cathode to the anode, with residual gas present in the device. When an electrical current is passed between the electrodes of one of the tubes, a glow can be seen in the chamber. Crookes tubes are glass vacuum chambers that contain a positive electrode (anode) and a negative electrode (cathode). It is not known precisely when Crookes began his work with the evacuated glass tubes that are commonly associated with his name, but it was presumably during his attempts to measure the weight of thallium in a vacuum. This instrument was the predecessor of a number of more sensitive types of radiant energy detectors. His investigations with the element also led to his discovery of the principle upon which he built the Crookes radiometer, a device that produces rotary motion from light. The discovery of thallium brought Crookes a significant amount of recognition and precipitated his election into the Royal Society of London in 1863. He chose the name of the element based on its bright green emission line, the Greek word thallos referring to "a young, green shoot" or "twig." He continued his study of thallium for many years, succeeding in isolating it, characterizing the properties of its compounds and eventually, in 1873, ascertaining its atomic weight. In 1861, when reexamining the residues he had saved from his early study of selenocyanides, Crookes discovered the element thallium through spectroscopic methods. Also in 1856, Crookes married Ellen Humphrey, who would bear him four children. From this laboratory, located in London, Crookes carried out a number of investigations, primarily in chemistry and physics.
His tenure at the school was brief since he soon gained a sizable inheritance from his father that enabled him to retire to his own private laboratory in 1856. Subsequently, in 1855, he began teaching chemistry at the College of Science in Chester. A sample of a deposit from a sulfuric acid factory was the source of the selenocyanides he studied.Īfter four years at the Royal College, Crookes accepted a position superintending the meteorological department of the Radcliffe Observatory at Oxford. His earliest published papers, which appeared when he was 19, recounted his work with selenocyanides, newly discovered compounds of selenium. In 1850, he began working as an assistant to August Wilhelm von Hoffman, which enabled him to undertake serious research. At the age of 15, Crookes enrolled at the Royal College of Chemistry, marking the beginning of a lifelong interest in the subject. William Crookes was born in London, England, on June 17, 1832, the son of Joseph Crookes and his second wife, Mary Scott.