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221 [334] LAVOISIER LAVOISIER
deeply in scientific research (was inti mately acquainted with Priestley [312] for instance), studied agriculture and ex perimented with new varieties of grain. He also studied and classified fossils un earthed in New York state at a time when the investigation of these objects was in its infancy. He was also an archi tect of considerable excellence. He was the closest approach to scientist-in-office among all the Presi dents of the United States. [334] LAVOISIER, Antoine Laurent (la-vwah-zyayO French chemist Born: Paris, August 26, 1743 Died: Paris, May 8, 1794 Lavoisier was born of a well-to-do family, was loved and pampered to an extreme, first by his mother and then, after her early death in 1748, by an adoring aunt, and was given an excellent education. This good fortune was not wasted, for the young man, suffering from chronic dyspepsia, devoted himself to his studies by both inclination and ne cessity, and proved a brilliant student. His father, a lawyer, hoped his son would follow in that profession, but young Lavoisier, who obtained his li cense in law in 1764, attended lectures on astronomy by Lacaille [284] and grew interested in science. After dabbling in geology, and doing creditable work in that field, he veered toward chemistry, and that became his life work. From the very beginning of his chemi cal researches he recognized the impor tance of accurate measurement. Thus his first important work, in 1764, lay in an investigation of the composition of the mineral gypsum. This he heated to drive off the water content, and he measured accurately the water given off. There were chemists before Lavoisier, notably Black [298] and Cavendish [307], who devoted themselves to measurement, but it was Lavoisier who pounded away at it until, by his very successes, he sold the notion to chemists generally. He did for chemistry what Galileo [166] had done for physics two centuries earlier and the effect on chemistry was just as fruitful. It is partly for this that Lavoisier is often called the father of modem chemistry and sometimes the Newton [231] of chemistry. Lavoisier was a most public-spirited citizen, joining numbers of boards and commissions designed to improve the lot of the people. In the 1760s he worked on improved methods of lighting towns (making a splash as a twenty-year-old with an essay on the subject), while in the 1770s he designed new methods for preparing saltpeter, a substance needed in the manufacture of gunpowder. These new methods made it unnecessary for government officials to ransack cellars and bams for crystals of the stuff, an in vasion of privacy that was sometimes brutally carried out and was strongly resented by the populace. In the 1780s he worked on the modernization of agri culture, and his researches involved a model farm he had established in 1778. All this public spirit was not to help him in the end, because of two mistakes. In the first place, he invested half a mil lion francs in the Ferme Générale in 1768 in order to earn money for his researches. The Ferme Générale was a private firm engaged by the French gov ernment, at a fixed fee, to collect taxes. Anything they collected over and above the fee they could keep. Naturally the “tax-farmers” gouged every last sou, and no group was more hated in eighteenth- century France than those same tax- farmers. Lavoisier himself was not en gaged in active tax-collecting, of course, but he worked busily in an adminis trative capacity. Nor did he use the money earned for selfish purposes but plowed it back into chemical research, setting up a magnificent private labora tory in which the scientific leaders of France regularly gathered. The envoys from the new republic across the sea, Thomas Jefferson [333] and Benjamin Franklin [272], were particularly wel come there. Nevertheless, Lavoisier was a tax- farmer and earned one hundred thou sand francs a year out of it. What’s more, in 1771 he married Marie-Anne, the daughter of an important executive
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of the Ferme Générale. She was young (only fourteen at the time), beautiful, and intelligent, and she threw herself wholeheartedly into his work, taking his notes, translating from English, illus trating his books, and so on. In general it was a splendid love-match, but she was the daughter of an executive tax- farmer.
Lavoisier’s second mistake involved the French Academy of Sciences, to which honored association he was elected in 1768, when only twenty-three. In 1780 a certain Jean-Paul Marat, a journalist who fancied himself a scientist, applied for membership and Lavoisier was active in blackballing him, for the very good reason that the papers he offered the academy (containing some foolish home-grown notions on the nature of fire) were worthless. Marat, however, was not the man to forget, and the time came when he was to take a fearful re venge. Lavoisier in the early, happy days was busily engaged in breaking down, one by one, the antique chemical notions that still cobwebbed the thinking of eigh teenth-century chemists. There were still some who maintained the old Greek notion of the elements and said that transmutation was possible be cause water could be turned to earth on long heating. This seemed so, for water heated for many days developed a solid sediment. Lavoisier decided, in 1768, to test the matter and boiled water for one hundred and one days in a device, called a “peli can,” that condensed the water vapor and returned it to the flask so that no water was lost in the process. And, of course, he employed his method of care ful measurement. He weighed both water and vessel before and after. Sediment appeared, but the water did not change its weight during the boiling. Therefore, the sediment could not have been formed out of the water. However, the flask itself had lost weight, a loss just equal to the weight of the sediment. In other words, the sediment was not water turning to earth, it was material from the glass, slowly etched away by the hot water and precipitating in solid frag ments. Here was a clear-cut example of the manner in which observation without measurement could be useless and mis leading.
Lavoisier’s interest in street lighting introduced him to the whole problem of combustion. The phlogiston theory of Stahl [241] had been in existence for a century now, and there were many things it could not explain. The resulting confusion among chemists was clarified by Lavoisier’s work and only after that clarification could chemistry move for ward (a second reason he is called the father of modem chemistry). Lavoisier began heating things in air in 1772. For instance, he and some other chemists bought a diamond and placed it in a closed vessel under the focused sun light of a magnifying glass. The diamond disappeared. Carbon dioxide gas ap peared within the vessel, proving the dia mond to be carbon or, at least, to con tain carbon. Lavoisier also took particu lar note of the fact that the diamond would not burn in the absence of air. Burning diamonds may seem pretty steep, just to prove a scientific point, but a prominent Parisian jeweler had made the claim that diamonds would not bum without air, and so confident was he of this and so anxious to prove himself right that he supplied the diamonds for the experiment and was willing to have one burned in the presence of air. Lavoisier went on to bum phosphorus and sulfur and to prove that the prod ucts weighed more than the original, so that he suspected some material had been gained from the air. (He didn’t be lieve phlogiston could have negative weight.)
In 1774, to test this point, he heated tin and lead in closed containers, with a limited supply of air. Both metals formed a layer of calx on the surface. The calx was known to be heavier than the metal it replaced, but Lavoisier found that the entire vessel (metal, calx, air, and all) was no heavier after the heating than before. This meant that if the calx represented a gain in weight, there must be a loss in weight elsewhere, possibly in the air. If that was so, then a partial vacuum must exist in the vessel.
[334] LAVOISIER LAVOISIER
Sure enough, when Lavoisier opened the vessel, air rushed in and then the vessel and its contents gained in weight. Lavoisier was thus able to show that the calx consisted of a combination of the metal with air, and that rusting (and combustion) did not involve a loss of phlogiston but a gain of at least a por tion of the air. When this notion finally made its way through the ranks of the chemists, it killed the phlogiston theory and es tablished chemistry on its modern basis. Furthermore, Lavoisier’s demonstration that mass was never altogether gained or lost but was merely shifted from one point to another in the course of chemi cal changes, is the law of conservation of mass, a bulwark of chemistry throughout the nineteenth century (and a third rea son why he is proclaimed father of mod ern chemistry). Einstein [1064] extended and refined the concept. In October 1774 Priestley [312] went to Paris. He visited Lavoisier and dis cussed his experiments with “dephlogis- ticated air.” Lavoisier repeated the ex periments and realized at once that the dephlogisticated-air notion was nonsense. Here instead was the portion of the air that combined with metals to form calxes. The very reason that objects burned so readily in the new gas was that it was undiluted by that portion of the air in which objects did not bum. By 1778 Lavoisier’s ideas were clear. He was the first to announce what other great chemists of the time, particularly Scheele [329], had only dimly sus pected: that air consisted of two gases, one of which supported combustion and one of which did not. In 1779 he called the former “oxygen” (from Greek words meaning “to give rise to acids,” because he believed that all acids contained this element, in which belief he was, for once, wrong). The latter he called azote (from Greek words meaning “no life”), but in 1790 it was named nitrogen by Chaptal [368] and that is the name it now bears. In one respect Lavoisier displayed a deplorable infirmity of character, for he avoided mentioning the help he had re ceived from Priestley and, without actu ally saying so, did his best to give the impression that he, himself, had discov ered oxygen. To be sure, Priestley’s help was not great and Lavoisier looked down upon Priestley as a mere tinkerer. Lavoi sier saw the true significance of Priest ley’s work which Priestley himself did not, so that Lavoisier deserves full marks for everything but the actual discovery of oxygen. However, it was the last bit of credit that he most coveted; he wanted to discover an element. He would do more for chemistry than any man before or since, but he would never discover an element. Lavoisier also studied the behavior of animals in air, in oxygen, and in nitro gen. He measured the amount of heat they produced and was able to show that life was very like combustion in that re spect. In 1783 Cavendish had shown that water could be formed by burning his inflammable gas in air. Cavendish, a con vinced phlogistonist, insisted on in terpreting this in terms of phlogiston. Lavoisier promptly repeated the experi ment in an improved manner and named the inflammable gas hydrogen (from Greek words meaning “to give rise to water”). This fitted in well with his new view of chemistry. He could see that when animals broke down foodstuffs (composed very largely of carbon and hydrogen), they did it by adding the ox ygen they breathed and forming carbon dioxide and water, both of which ap peared in the expired breath. Here, too, Lavoisier implied that the experiment of burning hydrogen was original with him. In fact, Lavoisier has such a dubious reputation as a credit snatcher that when it was discovered that a Russian chemist, Lomonosov [282], had published views like those of Lavoi sier a quarter century before the French man, some people began to wonder if Lavoisier had read Lomonosov’s works and didn’t bother to mention the matter. However, this is doubtful. The new chemistry began to catch on at once. In England, Hutton [297], Cav endish, and Priestley refused to aban don phlogiston, but Black [298] became a follower of Lavoisier. In Sweden, Berg
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man [315] went along with the new view, and in Germany, Klaproth [335]. At about this time, Guyton de Morveau [319] was trying to write an article on chemistry for an encyclopedia. He was having a miserable time trying to sum marize the knowledge of centuries and turned to Lavoisier for help. Lavoisier gave the problem some thought and de cided that the difficulty was a matter of language. (Guyton de Morveau had not accepted the new views of Lavoisier but, after collaborating with him for a while, he became another convert.) Having put chemistry on a new foun dation, Lavoisier went to work to give it a sensible language. The alchemists and early chemists had no fixed standard for naming the various chemical substances, and the alchemists, indeed, went out of their way to use obscure and fanciful names. The result was that no chemist could be sure exactly what another chemist was talking about. In collaboration with other chemists, including Berthollet [346] and Fourcroy [366], Lavoisier published a book, Methods of Chemical Nomenclature, in 1787. In this book were established the principles whereby every substance was assigned a definite name based on the el ements of which it was composed. The idea was that the name should indicate the composition. The system was so clear and logical that it was adopted by chem ists everywhere after some short-lived opposition on the part of a few phlogis- tonists. It still forms the basis of chemi cal nomenclature (a fourth reason why Lavoisier can be considered the father of modern chemistry). In 1789 Lavoisier went on to publish a textbook, Elementary Treatise on Chem istry, which served to present a unified picture of his new theories and in which he clearly stated the law of conservation of mass. It was the first modern chemical textbook (a fifth reason for his paternity of modem chemistry) and, among other things, it revived Boyle’s [212] notion of an element, and contained a list of all the elements then known; that is, all the substances that had not yet been broken down into still simpler substances. For the most part the list was quite accurate, and no material substance was listed that is not recognized today as ei ther an element or the oxide of an ele ment. However, Lavoisier listed light and heat as elements, though we now recog nize them to be nonmaterial. Lavoisier believed heat consisted of an “impon derable fluid” called “caloric.” He had eradicated one imponderable fluid, phlogiston, but it was partly through his influence that caloric, just as false, re mained in existence in the minds of chemists for a half century. Lavoisier extended his interest in com bustion into biology. From 1782 to 1784, with the assistance of the young Laplace [347], he tried to measure heats of combustion and work out some of the details of what went on in living tissue. In connection with these experiments, he made the first crude attempts at the anal ysis of compounds characteristic of liv ing tissue, something that was to be de veloped successfully by Liebig [532] a half century later. But in the same year that his textbook appeared the French Revolution broke out. By 1792 the radical antimonarchists were in control, France was declared a republic, and the tax-farmers began to be hunted down. Lavoisier was first barred from his laboratory and then arrested. When he objected that he was a scientist and not a tax-farmer (not quite true), the arresting officer is supposed to have responded with the famous remark, “The republic has no need of scientists.” (The republic quickly found out how wrong it was, as in the case of Chaptal and Le blanc [328].) The trial was a farce, with Marat— now a powerful revolutionary leader and eager for revenge—accusing Lavoisier of all sorts of ridiculous plots, such as that of “adding water to the peoples’ to bacco,” and wildly demanding his death. Marat was assassinated in July 1793, but the damage had already been done. Lavoisier (along with his father-in-law and other tax-farmers) was guillotined on May 8, 1794, and buried in an un marked grave. Two months later the rad icals were overthrown. His was the most deplorable single casualty of the revolu tion.
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LAMARCK [336] Lagrange [317] mourned: “A moment was all that was necessary to strike off his head, and probably a hundred years will not be sufficient to produce another like it.” Within two years of Lavoisier’s death, the regretful French were unveil ing busts of him. [335] KLAPROTH, Martin Heinrich (klap'rote) German chemist
ony, December 1, 1743 Died: Berlin, January 1, 1817 When Klaproth, the son of a tailor, was eight his family was impoverished as a result of a fire. At the age of sixteen he was apprenticed to an apothecary, which was, as Scheele [329] showed, an excel lent route to chemistry. Like Scheele, Klaproth rose from shop to shop and reached eminence, entering chemical re search on his own in 1780. (It didn’t hurt that in that year he gained eco nomic security by marrying the well-to- do niece of Marggraf [279]. He was one of the early converts to the new theories of Lavoisier [334] and this was important. Stahl [241], whose phlogiston theory Lavoisier had over thrown, had been a German and there was a nationalistic resistance to the new “French chemistry.” Klaproth helped break that down with conclusive experi ments in 1792. He made his own mark, however, mainly in the discovery of new elements. His first adventure in this direction proved to be the most meaningful. In 1789 he investigated a heavy black ore called pitchblende. He obtained a yellow compound from it that he was quite cer tain contained a hitherto unknown ele ment. He obtained the oxide of the metal—thinking it was the metal itself— and named it uranium after the fashion of the old alchemists who named metals after planets. The planet Uranus had been discovered eight years before by Herschel [321] and it seemed to Klap roth fitting to have a new metal named for a new planet. (A century and a half later, uranium, in the hands of Fermi [1243] and Hahn [1063], was to achieve an unexpected and grisly fame.) In that same year Klaproth also ob tained a new oxide from the semipre cious jewel the zircon, and named the new metal contained in the oxide “zir conium.” In 1795 he isolated the oxide of a new metal he named titanium (after the Titans of Greek mythology). Klap roth, unlike Lavoisier, was not covetous of honor and gave full credit to Gregor [377] for the initial discovery of this metal. On January 25, 1798, he was one of those instrumental in recognizing tel lurium to be a new element, but again he pointed out he was not the first to do so and in reporting on it he was careful to give credit to the original discoverer, F. J. Muller [323], Klaproth was hard on the heels of Berzelius [425] and Hisinger [390] in the discovery of cerium in 1803 and he was one of those who early showed the unex pected complexity of the rare earth min erals discovered by Gadolin [373]. This portion of his work was to be carried further by Mosander [501], Klaproth was one of the outstanding analytical chemists of his age and is sometimes referred to as the father of analytic chemistry. He was meticulous in his analytical work, publishing all his figures and making no attempt to adjust them in order to have them come out neatly, as even Lavoisier did on occa sion.
Klaproth was a pioneer in analytic chemistry and in the application of chemistry to archaeological objects, studying coins, glass, and ancient metal objects. When the University of Berlin was founded in 1810, Klaproth, although sixty-seven years old, was named its first professor of chemistry and served in that post until his death seven years later. [336] LAMARCK, Jean Baptiste Pierre Antoine de Monet, chevalier de French naturalist Born: Bazentin-le-Petit, Somme, August 1, 1744 Died: Paris, December 28, 1829 Download 17.33 Mb. Do'stlaringiz bilan baham: 
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