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536 [832] RAMSAY
RAMSAY [832] impure diamonds were reported by him and a sliver of colorless diamond, over half a millimeter in length, was exhib ited. The suggestion, nowadays, is that one of Moissan’s assistants, either in an effort to stop the miserable experiments, or as a practical joke (which was later too em barrassing to own up to), had slipped the sliver into the material being worked with. Others who attempted to make dia monds at that period, but without Mois san’s dubious success, were Crookes [695] and Parsons [850]. [832] RAMSAY, Sir William (ram'zee) Scottish chemist
hamshire, England, July 23, 1916 Ramsay, the son of a civil engineer, was an all-round man. As a youngster he was interested in music and languages and then developed further interests in mathematics and science. He was a man of athletic inclinations. To whatever he turned mind and hand, in that he did well. He was even a first-rate glass blower and made most of the apparatus he later used in handling the gases that brought him fame. He entered the University of Glasgow in 1866 and in 1871 studied chemistry in Germany under Bunsen [565], among others. He obtained his Ph.D. at the University of Tübingen. In 1880 he be came professor of chemistry at Univer sity College in Bristol and in 1887 he re ceived a similar position at University College in London, succeeding A. W. Williamson [650]. Although till then chiefly interested in organic chemistry (the constitution of alkaloids, particu larly), he grew intrigued, in 1892, by the problem posed by Rayleigh [760] in con nection with nitrogen and it was then that he approached the peak of his ca reer.
Rayleigh’s problem was that the nitro gen he obtained from air was a trifle denser than the nitrogen he obtained from compounds. Ramsay remembered reading that Cavendish [307], a century earlier, in a long-neglected experiment, had tried to combine the nitrogen of the air with oxygen and found that a final bubble of air was left over. It followed there might be a trace of some gas in air that was heavier than nitrogen and that did not combine with oxygen. So Cav endish had thought, at least. Ramsay repeated the experiment in more sophisticated fashion, trying to combine a sample of nitrogen obtained from air with magnesium. He too found a bubble of gas left over. But now Ram say had something Cavendish had not had—the spectroscope, which Kirchhoff [648] had introduced to chemistry a gen eration earlier. In 1894 Ramsay heated the gas and he and Rayleigh studied the lines produced. The strongest lines were in positions that fitted no known ele ment. It was a new gas, denser than ni trogen and making up about 1 percent of the atmosphere. It was completely inert and would not combine with any other element, so they named it argon, from a Greek word for inert. Since it combined with no element, it had a valence of 0. This, taken together with its atomic weight, seemed to indi cate that it belonged between chlorine and potassium in the periodic table. Chlorine and potassium both had valences of 1, so that the succession of valences was now 1, 0, 1, which was quite in the spirit of Mendeleev [705], the originator of the table. Moreover, if the periodic table could be accepted as a guide, argon had to be just one of a whole family of inert gases (or noble gases), each with a valence of 0. Such a family of elements, undreamed of by Mendeleev, would nevertheless fit into the periodic table rationally. Ramsay began the search. In 1895 he learned that in America, samples of a gas taken for nitrogen had been obtained from a uranium mineral. Ramsay re peated the work on a mineral called cleveite, named for Cleve [746], and found that the gas, when tested spectro scopically, showed lines that belonged neither to nitrogen nor argon. Instead, most astonishingly, they were the lines observed in the sun a generation earlier by Janssen [647]. Lockyer [719] had 537 [833] FISCHER
FISCHER [833] then attributed these to a new element he called helium, and now it turned out that helium existed after all, and right here on earth. Ramsay and his assistant searched for new gases in minerals. They failed. Then in 1898 they tried fractionating argon carefully after obtaining it from liquid air. They spent months preparing fifteen liters of argon and then they liquefied it and carefully allowed it to boil. The first fractions of gas contained a new light gas they called neon (“new”). The final fractions contained traces of two heavy gases which they named krypton (“hid den”) and xenon (“stranger”). The new column in the periodic table was filled, except for the lowest row, and that last place was filled two years later through studies in radioactivity. Ramsay himself grew interested in ra dioactivity, because that had been found to be a property of uranium and it was in uranium ores that he had found he lium. In 1903 he was able to show, in collaboration with Soddy [1052], that he lium was continually produced by natu rally radioactive products. When the final inert gas was discovered by Dorn [795]—the radioactive gas, radon—it was Ramsay who weighed a tiny quan tity of it and determined its atomic weight.
He was knighted in 1902 and, more important, he received the 1904 Nobel Prize in chemistry for his work on the inert gases. [833] FISCHER, Emil Hermann German chemist Born: Euskirchen, Rhenish Prus sia, October 9, 1852 Died: Berlin, July 15, 1919 Fischer’s father, a successful mer chant, wanted him to enter the family business (he was the one surviving son) but young Fischer, who finished at the head of his class at the Bonn high school in 1864, preferred science and easily demonstrated his lack of business talent. His father gave in and Fischer attended the lectures of Kekule [680] at the Uni versity of Bonn and later studied under Baeyer [718] and Kundt [744] at the University of Strasbourg. Fischer ob tained his doctorate in 1874 and went on to devote his professional life to extraor dinarily fruitful researches in various branches of organic chemistry. In 1875 he worked with organic deriv atives of hydrazine (a compound of ni trogen and hydrogen) and showed how they could be used to separate and iden tify sugars that, otherwise, were almost impossible to handle except as impure mixtures. His aptitude for chemistry was so clear by this time that his father de cided to be proud of him and saw to it that he remained financially secure. Fischer joined Baeyer, then went to the University of Erlangen in 1882 and to Wiirzberg in 1885. During the 1880s Fischer made use of his hydrazine compounds to isolate pure sugars and study their structures. He showed that the best-known sugars con tained six carbons and could exist in six teen varieties, depending on how the car bon bonds were arranged. Each different arrangement was reflected in the way the plane of light polarization was twisted, and he worked out exactly which ar rangement of carbon bonds applied to which sugar. In this way the practical observations of Pasteur [642] were com bined with the theory of Van’t Hoff [829], so that stereochemistry (the study of chemical structure in three-dimen sional space) was placed on a sound footing.
Fischer showed there were two series of sugars, mirror images of each other, which he called the D-series and the L- series. He had to pick which mirror image belonged to which possible method of writing the formula and did so arbitrarily. He had a fifty-fifty chance of guessing right, and recent work shows that he did guess right. The importance of stereochemistry to life is shown in the fact that just about all sugars in living tissue are of the D- series. The L-series virtually never ap pears in nature. Living tissue can tell them apart, so to speak, and prefers one series to the other. While doing all this, Fischer also worked with a class of compounds he 538 [834] BECQUEREL BECQUEREL
called purines, and elucidated their struc ture in detail. This turned out to be im portant, not just as an academic chemi cal exercise, but for the connection even tually discovered with the mechanism of life. Purines, as it turned out, are an im portant part of a group of substances called the nucleic acids, and these, it was discovered in the twentieth century, are the key molecules of living tissues. In 1892 Fischer moved to the Univer sity of Berlin as successor to Hofmann [604] after the latter’s death. In 1902 Fischer received the Nobel Prize for chemistry for his researches in sugars and purines, but this by no means meant that his life’s work was finished. He had shifted interest to the compli cated molecules of proteins. It was known that proteins were built up out of relatively simple compounds called amino acids, but Fischer showed exactly how these amino acids were combined with each other within the protein mole cule. Furthermore, he devised methods for linking one to another, in the same fashion that linkage took place in natural proteins. In 1907 he built up a very sim ple but quite authentic protein molecule made up of eighteen amino acid units and showed that digestive enzymes at tacked it just as they would attack natu ral proteins. This was a beginning in the complex field of protein structure, a type of work that was to culminate in the researches of Sanger [1426] and Du Vigneaud [1239] a half century later. Fischer’s final years were embittered by World War I, during which he orga nized German food and chemical pro duction for war, and in which he lost two of his three sons. In a fit of despon dency over the personal and national tragedy, and over the fact that he was suffering from cancer, he killed himself. [834] BECQUEREL, Antoine Henri (beh-krel') French physicist Born: Paris, December 15, 1852 Died: Le Croisic, Loire Inférieur, August 25, 1908 Becquerel, whose early schooling was as an engineer, obtained his doctorate in 1888 with a thesis on the absorption of light. He was a member of a family of physicists and his father was the A. E. Becquerel [623] who had done important work on fluorescence. Becquerel, in 1891, succeeded to the post at the Museum of Natural History in Paris that his father and grandfather had held before him. He continued the researches of his father and stumbled across something far more important, which, at a stroke, destroyed the nine teenth-century conception of atomic structure. The discovery of X rays by Roentgen [774] had intrigued Becquerel, as it had almost every physicist in Europe. View ing the discovery in the light of his own specialty, he wondered if any fluorescent materials might be emitting X rays. (After all, Roentgen discovered X rays by the fluorescence they brought about.) In February 1896 Becquerel wrapped photographic film in black paper and put it in sunlight with a crystal of a fluores cent chemical upon it. His reasoning was that if sunlight induced the fluorescence, and if the fluorescence contained X rays, then those X rays would penetrate the paper, as ordinary light and even ultravi olet light could not. (It was the pene trating power of X rays that was the most unusual property they possessed.) Becquerel used a chemical in which his father had been particularly interested— potassium uranyl sulfate. This was a compound containing uranium atoms, and it was this fluorescent material that Becquerel placed on top of his wrapped plates.
Sure enough, when the plate was de veloped, he found it to be fogged. This showed that radiation had penetrated the black paper, and Becquerel decided that X rays were indeed produced in fluores cence.
Then came a series of cloudy days and Becquerel could not continue his experi ments. By March 1 he was restless. He had a fresh plate neatly wrapped in the drawer, with the crystals resting on it, and there was nothing to do. Finally, un 539 [835] MICHELSON MICHELSON
able to bear the wait, he decided to develop the plates anyway. Perhaps a lit tle of the original fluorescence persisted and there would be some faint fogging, even though the crystals hadn’t been ex posed to sunlight for days. To his amazement, the plate was strongly fogged. Whatever radiation the compound was giving off did not depend on sunlight and did not involve fluores cence. Forgetting the sun, Becquerel began to study the radiation and found it quite like X rays, since it penetrated matter and ionized air. It continued to be given off by the compound in an unending stream, actively radiating in all directions. In 1898 Marie Curie [965] named the phenomenon radioactivity, a name that stuck. For a while the radia tion from uranium was called Becquerel rays, a term also introduced by Marie Curie. By 1899 Becquerel noted that the ra diation could be deflected by a magnetic field so that at least part of it consisted of tiny, charged particles. In 1900 he de cided the part that was negatively charged consisted of speeding electrons, identical in nature to those of the cath ode rays as identified by J. J. Thomson [869],
The only place the electrons radiated by uranium could be coming from was from within the atoms of uranium (which Becquerel identified in 1901 as the radioactive portion of the com pound). This was the first clear indica tion that the atom was not a featureless sphere but that it had an internal struc ture and that it might contain electrons. As a result of his discoveries Bec querel was awarded a share in the 1903 Nobel Prize in physics. The Curies also received a share. [835] MICHELSON, Albert Abraham (myTuil-sun) German-American physicist Born: Strelno, Prussia (now Strzelno, Poland), December 19, 1852
9, 1931
Michelson was four years old when his parents brought him to the United States. The family made its way out to the Far West, which was in the midst of its gold boom, and there they went into business rather than into mining. In his teens Albert applied for en trance to the United States Naval Acad emy. He had the backing of the Nevada congressman, who pointed out to Presi dent Grant the political usefulness of such a gesture to a prominent Jewish merchant of the New West. At the acad emy, Michelson shone in science but was rather below average in seamanship. He graduated in 1873 and served as a sci ence instructor at the academy in the lat ter part of that decade. He was not a particularly good teacher. In 1878 Michelson began work on what was to be the passion of his life, the accurate measurement of the speed of light. Roemer [232] had been the first to measure this two centuries earlier. Bradley [258], Foucault [619], and Fi- zeau [620] had done their bit, but Mi- chelson working with homemade appara tus was determined to do better than any of them. Using Foucault’s method, but adding some minor improvements, he made his first report on the velocity. Feeling that he had to study optics be fore he was qualified to make still fur ther progress, he crossed the ocean and studied in Germany and France. On his return to America he resigned from the navy and became a professor of physics at the Case School of Applied Science (now Case Western Reserve University) in Cleveland. In 1882 he was ready to try again and the result was a measure ment of the speed of light at 299,853 ki lometers a second (186,320 miles a sec ond), a value that remained the best available for a generation. (When it was bettered, it was Michelson who bettered it.) In 1881 Michelson was constructing an “interferometer” (with the financial help of A. G. Bell [789]), a device de signed to split a beam of light in two, send the parts along different paths, then bring them back together—an experi ment Maxwell [692] had suggested six years before. If they had traveled 5 4 0
[835] MICHELSON MICHELSON
different distances at the same velocity or equal distances at different velocities, the two parts of the beam would be out of phase and would interfere with each other, producing bands of light and dark. (It was these interference fringes that Thomas Young [402] detected when two rays of light met, and which had es tablished the wave nature of light.) Michelson put his interferometer to use by studying the two halves of a beam of light that were made to travel at right angles to each other. At that time it was considered that light, being a wave, had to be waves of something (just as the ocean waves are waves of water). Conse quently it was supposed that all space was filled with a luminiferous ether. (The word “luminiferous” means “light carrying” and “ether” is a hark-back to the fifth element that Aristotle [29] sup posed to be the component of all objects outside the earth’s atmosphere.) It was believed that ether was motion less and that the earth traveled through it. Light sent in the direction of earth’s motion ought therefore (or so it seemed) to travel more rapidly than light sent at right angles to it. The two beams of light ought to fall out of phase and show interference fringes. By measuring the width of the fringes it would then be possible to show the earth’s exact veloc ity when compared with the ether. In this way the earth’s “absolute motion” could be determined and the absolute motion of all bodies of the universe whose motions relative to the earth were known would also be determined. His first experiments in 1881, in Helmholtz’s [631] laboratory in Berlin, showed no interference fringes, but he continued to try with ever more elabo rate precautions against error, until in 1887 he and Morley [730] tried it under circumstances where it seemed they could not fail. Nevertheless, they failed. They could detect no fringes of significant width and therefore no difference in the velocity of light in any direction under any circumstances. (Nor has anyone else since that day.) The Michelson-Morley experiment, as it has always been known, is undoubtedly the most famous experiment-that-failed in the history of science. (Despite this, the introduction to the physics section in the catalog of the Uni versity of Chicago for 1898-1899 im plied that the structure of physics was so firmly placed that nothing further re mained to be done but to determine the sixth decimal place of various constants —this despite the fact that the Michel son-Morley experiment had knocked physics topsy-turvy. And who was the head of the physics department at the time? Why, Michelson!) The experiment overturned, particu larly, all theories involving the ether (Mach [733] said at once that the ether did not exist) and made it necessary to find some explanation for the invariance of the velocity of light. FitzGerald [821] came up with the most dramatic one, which involved slight changes in the lengths of objects at high velocities, changes which were just sufficient to mask any change in the velocity of light and thus make it seem to be constant. The climax came in 1905 when Einstein [1064] announced his special theory of Relativity, which began by assuming the velocity of light in a vacuum to be a fun damental and unvarying constant, and which wiped out the need for any ether at all by making use of the quantum theory that Planck [887] advanced in 1900. (Michelson, however, could never bring himself to accept relativity.) There is no doubt at all that the Michelson-Morley experiment served as the kicking-off point for the theoretical aspects of the Second Scientific Revolu tion, just as the discovery of X rays by Roentgen [774] in 1895 was to kick off its phenomenological aspects. In 1907 Michelson was awarded the Nobel Prize in physics for his optical studies generally. He was the first Ameri can to win a Nobel Prize in one of the sciences. But Michelson’s optical studies are not noted for negative results alone. His in terferometer made it possible for him to determine the width of heavenly objects by comparing the light rays from both sides and, from the nature of the inter ferences fringes, determine how far apart Download 17.33 Mb. Do'stlaringiz bilan baham: 
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