William Crookes

Sir William Crookes, OM , FRS (June 17 1832 – April 4 1919) was an English chemist and physicist. Sir William attended the Royal College of Chemistry in London, worked on spectroscopy.

In 1861 he discovered a previously unknown element with a bright green emission line in its spectrum and named the element thallium, from the Greek thallos, a green shoot. Crookes also identified the first known sample of helium, in 1895. He was the inventor of the Crookes radiometer, which today is made and sold as a novelty item. He also developed the Crookes tubes, investigating canal rays. In his investigations of the conduction of electricity in low pressure gases, he discovered that as the pressure was lowered, that the negative electrode appeared to emit rays (the so-called cathode rays, now known to be a stream of free electrons, and used in cathode ray display devices). As these examples indicate, he was a pioneer in the construction and use of vacuum tubes for the study of physical phenomena. He was, as a consequence, one of the first scientists to investigate what are now called plasmas. He also devised one of the first instruments for the study of nuclear radioactivity, the so-called spinthariscope.

Life

Early days

William Crookes was born in London, he was the eldest son of Joseph Crookes, a tailor of north-country origin, by his second wife, Mary Scott. William received some instruction at a grammar school at Chippenham, but his scientific career began when, at the age of fifteen, he entered the Royal College of Chemistry in Hanover Square, London, under August Wilhelm von Hofmann.

Rise as prominent chemist

From 1850 to 1854 he filled the position of assistant in the college, and soon embarked upon original work, not indeed in the region of organic chemistry whither the inspiration of his distinguished teacher might have been expected to lead him, but on certain new compounds of the element selenium, the selenocyanides. These form the subject of his first published papers in 1851.

Leaving the Royal College, he became in 1854 superintendent of the meteorological department at the Radcliffe Observatory in Oxford, and in 1855 was appointed lecturer in chemistry at the Chester training college. In 1856 he married Ellen, daughter of William Humphrey, of Darlington, by whom he had three sons and a daughter.

From this time his life was passed in London, and devoted mainly to independent work, journalistic, consulting, and academic. In 1859 he founded the Chemical News a science magazine, which he edited for many years and conducted on much less formal lines than is usual with journals of scientific societies.

English "Knight", role as president of scientific institutions and final days

After 1880 he lived at 7 Kensington Park Gardens, where in his private laboratory all his later work was carried out. Crookes's life was one of unbroken scientific activity. He was never one of those who gain influence by popular exposition; neither was he esoteric. The breadth of his interests, ranging over pure and applied science, economic and practical problems, and psychical research, made him a well-known personality, and he received many public and academic honours.

He was knighted in 1897, and in 1910 received the order of merit. At various times he was president of the Chemical Society, the Institution of Electrical Engineers, the Society of Chemical Industry, the British Association, and, from 1913 to 1915, of the Royal Society.

William died in London on April 4 1919, two years after his wife, to whom he had been much devoted.

Legacy

The work of Crookes extended over the regions of both chemistry and physics. Its salient characteristic was the originality of conception of his experiments, and the skill of their execution. It is probably just to say that his theoretical speculations, imaginative and stimulating as they may have been, were of less permanent importance.

Chemistry

He was always more effective in experiment than in interpretation. His first great discovery was that of the element thallium, announced in 1861. By this work his reputation became firmly established, and he was elected a fellow of the Royal Society in 1863.

The method of spectral analysis, introduced by Bunsen and Kirchhoff, was received by Crookes with great enthusiasm, and, on applying it to the examination of the seleniferous deposit from a sulphuric acid factory, he discovered an unknown green line in the spectrum. The isolation of the new metallic element, thallium, followed, and the investigation of the properties of its compounds, which are of great chemical interest.

Finally, in 1873, he determined the atomic weight of the new element in a research which is still a model of analytical precision. Two main lines of research now occupied the attention of Crookes for many years. These were the properties of rare gases, with which he began to occupy himself immediately, and the investigation of the elements of the "rare earths", upon which he embarked shortly after 1880.

His attention had been attracted to the first problem in using a vacuum balance in the course of the thallium researches. He soon discovered the phenomenon upon which depends the action of the well-known little instrument, the Crookes radiometer, in which a system of vanes, each blackened on one side and polished on the other, is set in rotation when exposed to radiant energy. He did not, however, provide the true explanation of this apparent "attraction and repulsion resulting from radiation".

For many years Crookes conducted laborious experiments on the elements of the rare earths, elements so similar to one another in chemical properties that special methods for their separation had to be devised. Throughout the work he employed spectroscopic methods for following the course, and testing the completeness, of the separation of one element from another. What had been one of the most obscure regions in inorganic chemistry gradually became clear.

In the course of the years during which he was thus occupied, Crookes was led to views on the existence of "meta-elements", or clusters of elements resembling one another so closely that in most ways the cluster behaves as a single individual. The "meta-elements" of Crookes bear a superficial resemblance to the mixtures of isotopes of which some elements are now known to consist; but the theory of meta-elements cannot justly be said to anticipate the discovery of isotopes, since it was based upon facts of a fundamentally different kind from those on which more recent views on isotopic elements are founded.

Crookes published numerous papers on spectroscopy, a subject which always had a great fascination for him, and he made researches on a large variety of minor subjects. In addition to various technical books, he wrote a standard treatise on Select Methods in Chemical Analysis in 1871, and a small book on Diamonds in 1909, a subject to which he had devoted some study during two visits to South Africa. He frequently served the government in an advisory capacity, and his work on the production of a glass which should cut off from molten glass the rays which are injurious to the eyes of the work-people, may be cited among his many public services.

Physics

Of more fundamental importance were his researches on the passage of the electrical discharge through rarefied gases. He found that as the attenuation of the gas was made greater the dark space round the negative electrode extended, while rays, now known as cathode rays, proceed from the electrode. He investigated the properties of the rays, showing that they travel in straight lines, cause phosphorescence in objects upon which they impinge, and by their impact produce great heat. He believed that he had discovered a fourth state of matter, which he called "radiant matter". But his theoretical views on the nature of "radiant matter" proved to be mistaken. He believed the rays to consist of streams of particles of ordinary molecular magnitude. It remained for Sir J. J. Thomson to discover their subatomic nature, and to prove that cathode rays consist of streams of negative electrons, that is, of negatively electrified particles whose mass is only 1/1800 that of the atom of hydrogen. Nevertheless, Crookes's experimental work in this field was the foundation of discoveries which have changed the whole conception of chemistry and physics.

William turned his attention to the newly discovered phenomena of radio-activity, Crookes, in 1900, achieved the separation from uranium of its active transformation product, uranium-X. He observed the gradual decay of the separated transformation product, and the simultaneous reproduction of a fresh supply in the original uranium. At about the same time as this important discovery, he observed that when "p-particles", ejected from radio-active substances, impinge upon zinc sulphide, each impact is accompanied by a minute scintillation, an observation which forms the basis of one of the most useful methods in the technique of radio-activity.

Spiritualism

In 1870 Crookes decided that science had a duty to study the preternatural phenomena associated with Spiritualism (Crookes 1870). Judging from family letters, Crookes had developed a favorable view of Spiritualism already by 1869 (Doyle 1926: volume 1, 232-233). Nevertheless, he was determined to conduct his inquiry impartially and described the conditions he imposed on mediums as follows: "It must be at my own house, and my own selection of friends and spectators, under my own conditions, and I may do whatever I like as regards apparatus" (Doyle 1926: volume 1, 177). Among the mediums he studied were Kate Fox, Florence Cook, and Daniel Dunglas Home (Doyle 1926: volume 1, 230-251). Among the phenomena he witnessed were movement of bodies at a distance, rappings, changes in the weights of bodies, levitation, appearance of luminous objects, appearance of phantom figures, appearance of writing without human agency, and circumstances which "point to the agency of an outside intelligence" (Crookes 1874).

Crookes' report on this research, in 1874, concluded that these phenomena could not be explained as conjuring, and that further research would indeed be useful. Crookes was not alone in his views. Fellow scientists who came to believe in Spiritualism included Alfred Russel Wallace, Oliver Joseph Lodge, Lord Rayleigh, and William James (Doyle 1926: volume 1, 62). Nevertheless, most scientists were convinced that Spiritualism was fraudulent, and Crookes' final report so outraged the scientific establishment "that there was talk of depriving him of his Fellowship of the Royal Society." Crookes then became much more cautious and didn't discuss his views publicly until 1898, when he felt his position was secure. From that time until his death in 1917, letters and interviews show that Crookes was a believer in Spiritualism (Doyle 1926: volume 1, 169-170, 249-251).

Trivia

In 1910 he was appointed as a Member of the Order of Merit by King Edward VII.
There is a portrait of Crookes by E. A. Walton in the rooms of the Royal Society, and another by P. Ludovici in the National Portrait Gallery NPG 1846

External links

Crookes, William. 1870. "Spiritualism Viewed by the Light of Modern Science." Quarterly Journal of Science. July 1870.
Crookes, William. 1874. "Notes of an Enquiry into the Phenomena called Spiritual during the Years 1870-1873." Quarterly Journal of Science. January 1874.
Doyle, Arthur Conan. The History of Spiritualism. New York: G.H. Doran, Co. Volume 1: 1926 Volume 2: 1926
Hinshelwood, Cyril Norman, "William Crookes, A Victorian man of science". 1927.
The Cathode Ray Tube site

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