Sir William Crookes, OM, FRS (1832-1919) was a British chemist and physicist who attended the Royal College of Chemistry, London, and worked on spectroscopy. He was a pioneer of vacuum tubes, inventing the Crookes tube. Crookes was the inventor of the Crookes radiometer, which today is made and sold as a novelty item.
Crookes made a career of being a meteorologist and lecturer at multiple places. Crookes worked in both the fields of chemistry and physics. The salient characteristic of his work was the originality of the conception of his experiments, and his skill in their execution. His interests, ranging over pure and applied science, economic and practical problems, and psychiatrical research, made him a well-known personality, and he received many public and academic honours. Crookes's life was one of unbroken scientific activity.
1832 June 17th. Born in London, the eldest son of 16. His father Joseph Crookes, was a tailor of north-country origin, living with his second wife, Mary Scott Lewis Rutherford Johnson.
From 1850 to 1854 he filled the position of assistant in the college, and soon embarked upon original work, not in organic chemistry where the inspiration of his teacher, August Wilhelm von Hofmann, might have been expected to lead him, but on new compounds of selenium. These formed the subject of his first published papers in 1851.
He worked at the department at the Radcliffe Observatory in Oxford in 1854, and in 1855 was appointed lecturer in chemistry at the Chester Diocesan Training College.
In 1856 he married Ellen, daughter of William Humphrey, of Darlington, by whom he fathered three sons and a daughter. Married and living in London, he was devoted mainly to independent work.
In 1859, he founded the Chemical News, a science magazine which he edited for many years and conducted on much less formal lines than his usual with journals of scientific societies. Middle years
In 1861, Crookes 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 wrote a standard treatise on Select Methods in Chemical Analysis in 1871. Crookes was effective in experimentation. The method of spectral analysis, introduced by Bunsen and Kirchhoff, was received by Crookes with great enthusiasm and to great effect.
1869 Wrote A Practical Treatise on Metallurgy. 
His first important discovery was that of the element thallium, announced in 1861, and made with the help of spectroscopy. By this work his reputation became firmly established, and he was elected a fellow of the Royal Society in 1863.
He developed the Crookes tubes, investigating cathode rays. He published numerous papers on spectroscopy and conducted research on a variety of minor subjects. In his investigations of the conduction of electricity in low pressure gases, he discovered that as the pressure was lowered, the negative electrode (cathode) 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 and identified it as the fourth state of matter in 1879. He also devised one of the first instruments for the study of nuclear radioactivity, the spinthariscope.
Crookes investigated the properties of cathode rays, showing that they travel in straight lines, cause fluorescence 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" were to be superseded. He believed the rays to consist of streams of particles of ordinary molecular magnitude. It remained for Sir J. J. Thomson to expound on the subatomic nature of cathode rays (consisting of streams of negative electrons). Nevertheless, Crookes's experimental work in this field was the foundation of discoveries which eventually changed the whole of chemistry and physics.
Crookes' attention had been attracted to the vacuum balance in the course of thallium research. He soon discovered the phenomenon upon which depends the action of 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. Crookes did not, however, provide the true explanation of this apparent "attraction and repulsion resulting from radiation".
After 1880, he lived at 7 Kensington Park Gardens, where all his later work was carried out in his private laboratory.
Crookes identified the first known sample of helium, in 1895. Crookes was knighted in 1897.
In 1903, Crookes turned his attention to the newly discovered phenomenon of radioactivity, achieving the separation from uranium of its active transformation product, uranium-X (later established to be protactinium). Crookes 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 sulfide, 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 radioactivity.
Crookes wrote a small book on diamonds in 1909. In 1910, Crookes received the Order of Merit.
1919 April 4th. Died in London, two years after his wife.
He is buried in Brompton Cemetery.
1919 Obituary 
SIR WILLIAM CROOKES, O.M., F.R.S., was born on the 17th June, 1832, and died on the 14th April, 1919.
He was the last of a small group of scientific "amateurs" who, during the last 50 years, devoted their means, opportunities and, in fact, their lives to scientific research. Warren De la Rue, William Spottiswoode, and William Crookes, all worked on the same lines: each at his own cost equipped laboratories, conducted important researches, became successively President of the Royal Society, and each lived to be able to look back upon his past labours with the consciousness of good work done and appreciated.
From the days when as a youth he worked in chemistry, photography, and astronomy, until his death Sir William Crookes had before him the pursuit of science as his main object, and this was coupled with a determination that no failure could thwart. The writer cannot recall a single instance when failure or mishap produced anything beyond a determination to try again—attention to the minutest detail characterized all Sir William's work.
The discovery of the element Thallium in 1862 and the laborious determination of its atomic weight was his first marked success, and from that time onward his work was a natural sequence of connected events. So that he might carry out the determination of the atomic weight of thallium to very great accuracy he had constructed a vacuum chamber to hold his balance, and when using this he was struck by the erratic behaviour of the balance when in a vacuum. This led to Ms researches on "Repulsion resulting from Radiation," and the ultimate invention of the so-called radiometer or light mill, an instrument familiar enough to everyone now, but only the writer knows the magnitude of the work and the hundreds of experiments that enabled the truth of its action to be evolved from the mass of fanciful speculation that followed the first observation of such novel motions.
It was about this period that Sir William has related a conversation that he had with Lord Kelvin, then Sir William Thomson, which ended in the latter's recommendation to "try electricity"; the trying of electricity led directly to those beautiful researches in "Radiant Matter" that will ever be associated with the name of Crookes. The lecture with the above title delivered at Sheffield in 1879 created a sensation in the scientific world, and was remarkable both for the beauty of the experiments shown and for the boldness of the speculations which accompanied them.
During the work on radiant matter the spectroscope was frequently employed to examine the brilliant radiations emitted by various solid substances under bombardment with cathode rays, and the occasional appearance of a bright citron-coloured band gave rise to a long research published under the title of "Radiant Matter Spectroscopy." This research extended from 1883 until a few years ago, and led to some very advanced and far-reaching reasoning upon the constitution of matter and the genesis of the elements.
At the British Association meeting in Birmingham in 1886 Sir William enlarged upon the difficulties of separating the various members of the "rare earth" elements, and in speculating upon the ultimate constitution of matter proposed the name "Protyle" for the "something that existed anterior to our elements." His investigations in radiant matter spectroscopy were at first wholly connected with the visible spectrum, entailing laborious observation on account of the faintness of the light. This suggested the hope that photography might be made to record the spectra with also the possibility that invisible bands in the ultra-violet region might be revealed. For this purpose a quartz spectrograph was constructed and became the starting-point of spectroscopic investigations that continued from about the year 1888 and were in full swing at the time of his death.
The first results of work with the quartz spectrograph was the discovery that the discontinuous phosphorescent spectrum extended far into the ultra-violet. Many bands showing details of construction exactly similar to those in the visible portion of the spectrum were observed ; one particularly fine group of bands was always found to accompany the fractions of the yttria earth series having an atomic weight of about 117, and work in chemistry aided with the spectrograph was concentrated in order to isolate the material. This was partly successful and caused Sir William (perhaps a little prematurely) to announce the discovery of a new element of the rare earth group to which he gave the name Victorium. This work was unfortunately never completed, and the matter remains for some future investigator to grapple with. The success with the first spectrograph, with two quartz prisms, led to the construction of a much larger instrument with a train of five prisms, and this apparatus, with a measuring micrometer constructed at the same time, has been used to record the arc and spark spectra of a great number of elements and some thousands of photographs have accumulated. In this brief outline of the labours of Sir William Crookes from the inside, a detailed account is not given of all the work of the past 50 years. This has been published elsewhere; the number of "papers" amounts to some hundreds, for Sir William was an indefatigable worker. Except for a brief holiday in the summer, week in, week out, he was constantly in his laboratory. It was one of his favourite sayings that a man should always have a little more to do than he could possibly accomplish, and this became true in his own case, for death came before he had ceased working, and he has left many things undone. His last paper on "The Arc Spectrum of Scandium" has just been published in the Proceedings of the Royal Society.
As the end approached, bringing much pain, there was never a murmur of complaint, and he remained bright and kindly until the last. He continued to come down into his study until within the last few days, and then like a tired child laid down and passed quietly away. His list of honours and distinctions was a large one, but while keenly appreciating the public recognition of his labours he cared very little for insignia, which were mostly stowed away in a drawer in the corner of his study and, except for the Order of Merit bestowed upon him in 1910, were rarely brought into the light.
He was elected a Member of the Institution in 18S1 and was President in 1891.
1919 Obituary 
Sir WILLIAM CROOKES, O.M., F.R.S., Honorary Member since 1916, died on April 5, 1919, aged eighty-six years, at his residence in London.
He was born in London on June 17, 1832. His chief object in life was scientific work. Possessed of a seemingly innate love of science, he played at chemistry in his early childhood, and at the age of ten had set up a little laboratory. Research and the progress of science continued to be the dominating interest throughout his. long life, his remarkable powers of scientific research being exercised almost to the last.
At the age of eighty-three, though already busily engaged on Committees of the Royal Society and the Chemical Society, he joined the Admiralty board of Invention and Research, thus, still further placing at the disposal of his country his great knowledge and wonderful gifts. His professional career began in 1848, when he entered the Royal College of Chemistry as a student of Dr. Hoffman.
In 1854 he threw up a coveted meteorological position in order to devote himself to chemistry, and a few years later he accomplished his first discovery, which brought him immediate fame - a discovery of metallurgical as well as of chemical interest. He had already made himself an adept in the use of the spectroscope, in those days a new instrument of research.
In 1861, while conducting with the spectroscope an examination of the residue which is left in the manufacture of sulphuric acid, he observed in the spectrum a pale green line that he had not noticed previously, and following up the suggestion he eventually isolated a new metallic element, to which he gave the name of thallium. A specimen of this till then unknown constituent of Nature was shown at the Exhibition of 1861, and commanded universal attention.
For the greater part of the next eight years Crookes engaged himself in the investigation of the properties of this substance. That assiduous attention to the one line of inquiry until it was carried as far as it could be was characteristic of the man, and the key to his success. As he has said: "To stop short in any research that bids fair to widen the gates of knowledge, to recoil from fear of difficulty or adverse criticism, is to bring reproach upon science."
Thallium led to another triumph in an unexpected manner. While attempting to ascertain its atomic weight - a difficult operation with any element - he placed his balance in a vacuum, and then discovered that, under these conditions, the metal appeared to be heavier when cold than when heated. The difference he explained by a "repulsion arising from radiation" that is to say, that the heated body in a vacuum had a tendency to repel itself from another body, which was still hotter than itself. This led to the study of vacua, which ultimately had issues of the highest value. The first outcome was the invention of the radiometer, that little instrument to be seen in opticians' windows, and with which most persons are familiar, in which delicately suspended vanes revolve in an exhausted glass bulb. They are caused to spin round, apparently by light, but really by heat, acting on the residual gas left in the bulb.
From this invention Crookes proceeded to examine the passage of electricity through high vacua tubes from which as much as possible of the air had been withdrawn. The results were very remarkable. Peculiar electrical effects and brilliant bands of colour were obtained, and the exhibits were themes of wonder at the Royal Society's conversaziones for some years in the 'eighties. To the inventor himself they suggested " a fourth state of matter," the ultra-gaseous, something on the border-line between common matter and electricity - a sort of fringe where substance and force seemed to merge into one another.
His speculations anticipate by nearly a quarter of a century some of the most startling of modern advances in physics. His "radiant matter" developed into the electrons of Dr. Johnstone Stoney ; and Sir J. J. Thomson has worked out from these a corpuscular theory of matter, much of this advance being due to Crookes' speculations, and still more to Crookes' tube, which is now an instrument of research everywhere. It was this famous tube that made the discovery of the Röntgen rays possible, and Sir William narrowly' missed making that discovery himself.
During an experiment with a camera and one of his tubes he noticed, on developing the plates, that certain marks, corresponding to his fingers, appeared on the films, and thinking this was due to defective plates he returned them to the makers with some strong remarks. Had he thought that the tube might have produced the image he must have been the discoverer of the X-rays, for this experiment took place sometime before Rontgen's. The supposed faulty plate contained probably the first picture ever produced by X-rays.
Radium has confirmed another of Sir William's theories - namely, that the elements of which the universe is built up are derived by a process of evolution from some form of primordial matter, which provisionally he named "protyle." If this hypothesis were true, the elements would have to be regarded as built up of still smaller bodies. The discovery of radium, and the evidence of its breaking up into a variety of rays and producing helium, led physicists at once to revise their opinions, and now most of the elementary atoms of former days are regarded as merely intermediate forms, derived from others,' and themselves probably breaking up into others.
Professor F. Soddy, in his 1919 May Lecture to this Institute, has well set forth the confirmation of Sir William's theories, which he amplifies and elaborates. Crookes owed much of his success, both as chemist and physicist, to his early scientific training, and this was seconded by mental qualities of a high order. He was a patient, indomitable investigator ; he took broad views of science, more than once propounding theories in advance of his time ; and he had the happy gift of invention, as was shown in his radiometer and famous tube. Hardly had radium been seen in this country when Crookes invented the spinthariscope, which enabled its otherwise invisible scintillations to be seen.
He succeeded, in 1908, in effecting the first complete separation of scandium from the rare earths in which this element occurs. The method of separation was extremely laborious, but eventually Sir William was able to secure spectrum photographs showing fine groups of the characteristic red scandium lines quite free from those of any other body. He determined the atomic weight of the metal as 44.1-- a figure which agrees with Mendeleeff's table, who gave a description of a hypothetical element, " ekaboron," of atomic weight 44, which resembles scandium.
As a chemist Sir W. Crookes had a wide range. of interests, as shown by his publications, among which were, " Select Methods in Chemical Analysis," " Manufacture of Beetroot Sugar in England," " Handbook of Dyeing and Calico Printing," " Dyeing and Tissue Printing," " Keel's Treatise on Metallurgy," " Wagner's Chemical Technology," " A Solution of the Sewage Question," " The Profitable Disposal of Sewage," and " The Wheat Problem."
In 1859 he founded the Chemical News, and had edited it ever since. He had been honoured for his scientific achievements both at home and abroad. In 1880 he received from the French Academy of Sciences their gold medal and a purse of 3000 francs ; his portrait was presented to the Royal Society, and in 1885 the Davy medal of the Royal Society was bestowed upon him. He was President, and three times the Bakerian lecturer, of the Royal Society. The Universities of Oxford, Cambridge, Sheffield, Durham, the Cape, and Dublin conferred upon him their degree of D.Sc., and he was an LL.D. of Birmingham. Hg was a Fellow, a former member of the Council, and an ex-President of the Royal Society, of which he was also a Royal Medallist. In 1897, on the occasion of Queen Victoria's Diamond Jubilee, he was knighted, "in recognition of the eminent services he had rendered to the advance of scientific knowledge during her Majesty's reign," and in 1910 the coveted honour of the Order of Merit was conferred on him.