THE DISCOVERY OF THE ELEMENTS. VI. TELLURIUM AND SELENIUM* Mnnv ELVIRA WEEKS, THEUNIVERSITY OF KANSAS, LAWRENCE, KANSAS
I t has been shown i n the three preceding articles** that a number of elements including zinc, cobalt, nickel, manganese, hydrogen, nitrogen, oxygen, tungsten, molybdenum, and chromium were recognized and isolated during the eighteenth century. The story of tellurium, its discovery by Baron Mziller von Reichenstein and its confirmation by Klaproth remains to be told. Although selenium properly belongs in the early part of the nineteenth century, i t i s so closely related to tellurium both chemically and historically that i t seems best to introduce i t at this point. The scientifLc contributions and correspondence of Klaproth and Berzelius furnish detailed information about these huo great discoveries, and the "&rly Recollections of a Chemist" by Friedrich Wohler present a n unforgettable picture of the great Swedish master. . . . . . . "The chymists are a strange class of mortals impelled by a n almost insane impulse to seek their pleasure among smoke and vapour, soot and &me, poisons and poverty; yet among all these evils I seem to live so sweetly, that may I die if I would change places with the Persian King." (1) The discoverer of tellurium, Franz Joseph Miiller, was born on June 1, 1740, in Vienna, where his father served as the Transylvanian treasurer, or Thesauriatsrath. After studying law and philosophy in his native city, Franz Joseph went to the School of Mines at Schemnitz, where he became intensely interested in mining, mineralogy, chemistry, and mechanics. At the age of twenty-eight years he became a surveyor in Hungary, and two years later he served so efficiently on a committee which managed the mines and smelters in the Banat that he was appointed surveyor and director of the mines. In 1775 he went to the Tyrol as mine captain and acting superintendent, and under Joseph I1 he became chief inspector of all the mines, smelters, and salt-works in Transylvania (2). In 1782 Miiller extracted from a bluish-white ore of gold (called aurum problematicurn, aurum paradmum, or aurum album), a metal which he at iirst thought to be antimony. In fact his paper announcing the discovery was entitled, "An Experiment with the Regulus Thought to Be Metallic Antimony Occurring in the Mariahilf Mine on Mt. Fazebay near Salatna."t Upon further examination of the regulus, he decided that, although the metal bore some resemblance to antimony, it must he a new element, different from all others. Seeking confirmation of his discovery, he sent a
* Illustrations by F. B. Dains. The University of Kansas, Lawrence,Kansas. * * S e e J. CHEM. EDUC.,9, 2 2 4 0 (Jan., 1932); 215-35 (Feb., 1932); see also pp 459-73 of this issue. t "Vwsuch mil dem i n dcr Grubs Mariahilf i n dem Gebirge Fezebay bei Selatm vorkommenden unmcintm gediegenen Spiessglaskdnig." 474
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tiny specimen to Bergman; but with such a small sample, the latter could do no more than prove that it was not antimony ( 3 ) , (11). Miiller's important discovery seems to have been overlooked for sixteen years, but on January 25, 1798, Klaproth read a paper on the gold ores of Transylvania before the Academy of Sciences in Berlin. In his address he reminded his hearers of the forgotten element, and suggested for it the name tellurium, meaning enrth, by which it has ever since been known ( 3 ) . It is hard From "Jac. Bwmlius, Selbrthiogmphischr A~fecichnungn" to understand why so ~ ~ h~ r b ~rm'r ~ ~ m a n y historians of YOUTHFUL PORTRAIT ox BERZELIU~ science credit him with Left an orphan early in life, he was educated by his the discovery of tellu- grandfather. Berzelius studied at the Linktiping Gymrium. Klaproth, who nasium and later at the University of Upsala, where he the degree of Doctor of Medicine. He was a was never desirous of received student of Ekeberg, the discoverer of tantalum. undeserved honors, stated definitely that the element had been discovered by Miiller von Reichenstein in 1782 (11). Klaproth isolated tellurium from the gold ore by the following method. After digesting the pulverized ore with aqua regia, he filtered off the residue and diluted the filtrate slightly with water. When he made the solution alkaline with caustic potash, a white precipitate appeared, but this dissolved in excess alkali, leaving only a brown, flocculent deposit containing gold and hydrous ferric oxide. Klaproth removed this precipitate by filtration and added hydrochloric acid to the filtrate until it was exactly neutral. A copious precipitate appeared. After washing and drying it, he stirred it up with oil and introduced the oil paste into a glass retort,
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which he gradually heated to redness. When he cooled the apparatus, he found metallic globules of tellwium in the receiver and retort (3), (11). The discovery of tellurium was by no means the only service that Miiller von Reichenstein performed for the glory of his country. Kaiser Joseph appointed him acting governor (Gubernialratlz) and raised him to the hereditary nobility with the title of Freiherr (Baron) von Reichenstein. For sixteen years he was a courtier in Vienna, but in 1818 he asked permission to retire. Although he was exempted from making reports, he was still asked to attend all the council meetings, in order that the state might continue to receive his valued advice on mining and metallurgy. The cross of the Order of St. Stephan was awarded to him for distinguished services to his country and he was also elected to membership in the Mining Society, the Gesellschaft mturforschender Freunde (Society of Scientific Friends) at Berlin and in the Mineralogical Society at Jena (2). After serving his country for sixty-two years and publishing many contributions to chemistry and mineralogy, Miiller von Reichenstein died in Vienna, the city of his birth, at the venerable age of eighty-five years (4). According to Paul Diergart, Paul Kitaibel, professor of botany and
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chemistry a t the University of Pest, discovered tellurium independently in 1789 and wrote a treatise on it (5). Selenium The discoverer of selenium was no other than the illustrious Swedish chemist, Jons Jakob Berzelius, who was born in Wafversunda, a village in East Gothland, on August 20, 1779. His childhood was saddened by the early death of his parents, but his grandfather provided carefully for his education. After attending the school at Linkoping, Berzelius studied medicine at Upsala, and at the age of twenty-two years he received his medical degree. Afzelius, a nephew of Bergman, was then the professor of chemistry, and Ekeberg, who discovered tantalum a t about the time of Berzelius' graduation, was an assistant. t I n the following year Berzelius was a p p o i n t e d assistant professor of medi- $ cine, botany, and pharmacy a t the University of Stock- + .., holm, a position in which he + served with honor and distinction for the rest of his 2 life. During part of the , time he also lectured a t the Military Colleae - and a t the Medico-Surgical Institute FIRST-FLOOR PLANOP BERZELIUS'LABORATORY AND DWELLING HOUSE a t Stockholm. Berzelius, 1-Kitchen-Laboratory unlike other chemistry pro2-Laboratory 3 -Bedroom fessors of his time, enlivened 4-Parlor his lectures with many strik5-Barn i n g demonstrations. H i s fame as a teacher soon spread throughout Europe, with the result that brilliant ambitious students of chemistry made Stockholm their Mecca. Mitscherlich, Wohler, C. G. Gmelin, Mosander, Svanberg, Sefstrom, and the Rose brothers, Heinrich and Gustav, all received their inspiration from the great Swedish master. A vivid picture of Berzelius and an understanding of his sympathetic attitude toward his students may be obtained by reading the "Early Recollections of a Chemist" by Friedrich Wohler:
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With a throbbing heart (says Wohler) I stood before Berzelins's door and rang the bell. A well-dressed, dignified gentleman with florid and healthy complexion let me in. It was Berzelius himself. He welcomed me very cordially, informed me that he had been ex-
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pecting me for some time, and wished me to tell him of my journeyall this in the German language, with which he was as familiar as with French and English. This first day he took me to the Caroline Institute, where he gave his lectures to medical students, but which were also attended by officers of the army and several of his friends, and which I regularly visited afterwards to accustom my ear to the language. This afforded me opportunity to admire his calm and clear delivery and his skill in performing experiments. In this institute was also the laboratory for medical students, which was presided over by Mosander (6). Berzelius determined t h e atomic weights of nearly all the elements then known, and was the first chemist to determine them accurately. He referred his atomic weights to oxygen, which, however, he allowed to equal 100, instead of 16 as in our present system. I n his little laboratory that looked like a kitchen and in which the sandbath on the stove was never allowed t o cool, Berzelius discovered the important elements: selenium, silicon, thorium, cerium, and zirconium. .A omid ~ l r r i r hby rllcrpnrcr brother ed..rd. mufmonn.i ..zar Erin: About a hundred miles north"""""X 0% YO'R"&V'Y""6e"" P ~ c u ~ ~ E " Of Stockholm there lies GUSTAV MAGNUS, 1802-1870 among barren hills the famous German chemist and physicist. One of Oldmining-town of ~ ~ h ~h~ l ~ Berzelius' distinguished students. He was F e of the first chemists to investigate tellunum. Hecontrihutedtomineralogicalchemical analysis, physiological and agricultural chemistry and chemical technology, and devised a simple process for recovering selenium from the slime in the lead chambers of sulfuric acid ~ l a n t s . He also carried out im~ortant rese2ches in mechanics, hydrodynamiG, heat, optics, electricity, and magnetism.
average tourist would not be greatly interested in the smoky old town with its grimy, little houses, its sickly vegetation, and its odor of sulfuric acid but the chemist would
recall its imnortant rBle in the early history of selenium. Berzelius and Assessor Gahn owned shares in a sulfuric acid plant a t Gripsholm that used as raw material pyrite from the mine a t Fahlun. On September 23, 1817 (7), Berzelius wrote to his friend, Dr. Marcet of London, that he and Gahn had found tellurium in the sulfuric acid, but on February 6th of the following year he wrotc again to Dr. Marcet, telling him that they had been mistaken about the tellurium (8).
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I have just examined i t more carefully here a t Stockholm (wrote Berzelius) and have found that what Mr. Gahn and I took for tellurium is a new substance, endowed with interesting properties. This substance has the properties of a metal, combined with that of sulfur t o such a degree that one would say i t is a new kind of sulfur. Here are some of its properties. . . . If one sublimes i t in a large vessel, i t is deposited in the form of flowers of a cinnabar red, which are nevertheless not oxidized. During its cooling i t keeps for some time a certain degree of fluidity, such that one can shape i t between the fingers and draw it into threads.. . . When one heats this new substance with a flame, it burns with an azure blue flame, and gives a very strong odor of radishes; i t was this odor that made us think it was tellurium. The similarity t o tellurium has given me occasion to name the new substance selenium.. . . I n the hope of pleasing you and Mr. Wollaston, I am enclosing a little thread of selenium, which will surely be broken before arriving, but some of i t will always remain. The paper in which i t is wrapped has been colored by a sublimation of selenium which took place when, in my absence, the fire was stirred u too much in order t o evaporate a solution of ammonium selenate f8). The following long quotation from Berzelius not only gives the details of this remarkable discovery, but also s e w as a splendid example of his vividly clear literary style:
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THEFAHLUN MINEIS THE OLDESTCOPPERMINEIX SWEDEN I t was worked in the 13th century, and has been rnn almost continually ever since. Its present output of copper is small, but iron pyrite is still produced. The pyrite from this mine was the first source of selenium. Gahn, the discoverex of manganese, and Sefstrdrn, the discoverer of vanadium, resided in Fahlun.
They use a t Fahlun (he said) for the manufacture of sulfur, pyrites occurring a t various places in the copper mine. The pyrites are often mixed with galena, blende, and several foreign substances. The pyrites are placed on a layer of dry wood, in long, horizontal furnaces, the upper part of which is covered with earth and decomposed pyrites; the fumes pass from these furnaces into horizontal tuyeres, the fore part of which is of brick and the rest of wood. The wood is lighted below, and the heat causes the excess sulfur to distil from the lower layer of the pyrite; the gaseous sulfur is carried bv the current of warm air. and is finallv de~ositedas flowers in the tuyeres.. . When this distilled sulfur is used for manufacturing sulfuric acid by burning it, a red, pulverulent mass is deposited at the bottom of the lead chamber. This fact was observed long ago by Mr. Bjuggren, who then owned a sulfuric acid plant at Gripsholm. He found that this does not occur when another k i d of sulfur is used; and as he had learned from a chemist that the red material must contain arsenic, he no longer used sulfur from Fahlun. Since this plant has been purchased by Gahn, Eggertz and myself (continued Berzelius), the Fahlun sulfur has been burned there continually. The red sediment which forms in the acid liquid always remained a t the bottom of the chamber, and consequently increased in thickness to the depth of a millimeter. The operation by which the sulfur is acidified in this plant differs from that usually employed
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in that the sulfur is not mixed with potassium nitrate. Flat glass vessels containing nitric acid are placed on the bottom of the tank and the sulfurous acid gas, in decomposing the nitric acid, produces the nitrous gas necessary for the complete acidification of the sulfur. . . Berzelius then explained how he and Assessor Gahn had been misled into thinking that they had found tellurium in the sulfuric acid. In the glass vessels containing the nitric acid (said he) there is found, after the complete decomposition of the nitric acid, a conceutrated sulfuric acid a t the bottom of which is deposited a red, or sometimes brown, powder. This powder aroused our attention and led us to make a special examination of it. The quantity resulting from the combustion of 250 kilos of sulfur did not exceed 3 grams. The principal mass was sulfur; i t could be lighted and burned like this substance; but i t left a copious ash which, when heated with a blowpipe, gave a strong odor of decaved radishes or cabbacce, analog~~~ to that which ~ l a @ o t hsays is produced when one treats tellurium in the same manner. . . . The appearance of a substance as rare as tellurium in the Fahlun sulfur led me to try to isolate it, in order to obtain more exact and certain ideas regarding it. I therefore had the whole mass a t the ALEXAND~BMARCBT 1770-1822 bottom of the lead chamber reSwiss physician and chemist. Lecmoved. While still wet i t had a turer on at Guy,s Hospital, reddish color, which, upon desk~ ~ ~ ~~ of ~ i d ~ ~ ~wollas~ ~ ~d ~ cation, became almost yellow. It tan, and Tennant. He carried out a weighed about four pounds. It number of researches in physiological was treated with aqua regia added chemistry. In collaboration with Berz d i ~he~ studied the properties of in suficient quantity to render the carbon bisulfide. mass pulpy, and was finally digested a t a moderate temperature. It gradually changed color, the red disappeared, and the mass became greenish yellow. After 48 hours of digestion, water and sulfuric acid were added, and i t was filtered. The filtrate had a deep yellow color. The mass remaining on the filter had not visibly diminished in volume; it consisted principally of sulfur mixed with lead sulfate and other impurities. The fmal steps in the isolation of the new element were described by Berzelius as follows: A small quantity of filtrate (said he) was taken to study the method of separating the substance supposed to be present; it was pre-
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cipitated with ammonium hydroxide. The precipitate, well washed and dried, mixed with potassium and heated a t the end of a barometer tube, decomposed with ignition. Placed in water, a part dissolved, and the liquid acquired the orange color of strong beer, very different from the red wine color given by the hydrotelluride of potassium. The liquid did not cover the silvery pellet which always rises to the surface of the hydrotelluride of potassium; but after a few hours, i t became turbid and deposited red flakes, the quantity of which was increased by the addition of nitric acid. The precipitate was preserved, and when a part of the filter on which the red precipitate had been collected was lighted a t a candle flame, i t gave the edges of the flame an azure blue color, meanwhile exhaling a strong odor of putrid cabbage. A portion of very pure tellurium, precipitated in the same manner from a solution of the hydrotelluride of potassium, had a gray color, gave a greenish color to the edge of the flame, and produced no perceptible radish odor. . .. Berzelius then proved that the odor of impure tellurium is caused by the presence in i t of small amounts of the new substance. Upon examining more carefully the purified tellurium which served for my earlier experiments with the oxide of tellurium and hydrogen telluride gas (said he) I found that it produced no odor, either when one heated i t with the blowpipe or upon reduction to the oxide, and that the only way to make i t produce such an odor was to heat i t in a glass tube closed with the finger, until the vaporized metal escaped through a hole in the softened glass. It then burned in this hole with a blue flame, giving an odor entirely analogous to that of the red substance. . . . These experiments seemed to me to prove that the red substance could not be tellurium, but that tellurium itself contains varying amounts of i t according to the care with which i t has been purified. . . . Berzelius continued his experiments and soon realized that he was dealing with a new element. The brown material, insoluble in water, examined more carefully (said he) was recognized to be the cause of the peculiar odor we mentioned above; and by means of some experiments which we shall report soon, it was found that i t was a combustible, elementary substance hitherto unknown, to which I have given the name selenium, derived from Selene (the moon), to recall its analogy with tellurium. According to its chemical properties, this substance belongs between sulfur and tellurium, although i t has more properties in common with sulfur than with tellurium (9). Since Klaproth had named tellurium for the earth, Berzelius thought i t appropriate to name the sister element for the earth's satellite. The results of his investigation of selenium and its compounds were published in 1818 in the Annules de Chimie et de Physique.
Repmducad b r hind ~ e r m i r s i o nof The Edgar P. Smilh Memorial Collcciion i n the Ilirfory of Chcmislry, Uniueraiiy of Pennrylvanio
B s n z E ~ I u sAUTOGRAPH LETTER
Translation of Letter, Part of Which Is Reproduced Aboue Letter of Introduction written by Berzelius for Mr. Engelke to Herr E. L. Schubartz (?), PhD.. M.D., Professor Extraordinary of Chemistry a t the University of Berlin and Teacher of Chemistry a t the Technical Institute in Berlin. Stockholm, Apr. 14,1815. Dear Su: I herewith take the liberty to commend t o you heartily Mr. Engelke, the hearer of this letter. Mr. Engelke is, to he sure, really neither a scientist nor a technoloaist: he
fo;eign.muntries from 'the point of view of'politifal economy; and indeed I could recommend him t o no other than yourself with greater hope that he would receive sound m l i h n c e in these thing3 I should thcrrfore drrm it a F r a t favor if you w o ~ ~ have l d tlw kindnws to receive my friend I
