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[411] STROHMEYER, Friedrich (shtroh'my-er) German chemist
gust 2, 1776 Died: Gottingen, August 18, 1835 Strohmeyer, the son of a professor of medicine, began his education in Gottin gen, his father’s school, but the final touch was added in Paris, where he stud
[412] AVOGADRO
AVOGADRO [412] ied under Vauquelin [379]. He followed in the footsteps of Vauquelin as to his field of specialization and remained a mineralogist throughout his career. (This contagion of specialty is by no means a general rule. Strohmeyer’s own most prominent pupil, Gmelin [457], devel oped much wider interests.) In 1802 he joined the faculty of the University of Gottingen and by 1810 was a full professor of chemistry. He was one of the first to offer laboratory instruction in chemistry, though he was soon to be overshadowed in this respect by Liebig [532]. The most important dis covery of his life did not come about through his strictly academic work, how ever. He also doubled as inspector general of apothecaries in Hannover. In 1817, fulfilling the duties of this office, he came across an apothecary’s shop in which a bottle labeled zinc oxide con tained zinc carbonate. Following this up, Strohmeyer found himself interested in zinc carbonate, which turned yellow on strong heating as though it contained iron as an impurity, yet it contained no iron. He traced the yellow to an oxide not of zinc but of a hitherto unknown metal rather like it chemically. He named it cadmium from the Latin name for a zinc ore in which it is usually found accompanying the zinc. [412] AVOGADRO, Amedeo, count of Quaregna (ah-voh-gah'droh) Italian physicist Born: Turin, Piedmont, August 9, 1776
Died: Turin, July 9, 1856 Avogadro was born into a family of lawyers and succeeded to his father’s title in 1787. In 1796 he received a doc torate in law and practiced for three years before turning to science. A pro fessor of physics at the University of Turin in later life, Avogadro suffered the not-too-uncommon fate of neglect in his lifetime and success after death. Avogadro considered the discovery made by Gay-Lussac [420] that all gases expand to the same extent with rise in temperature and decided that this must signify that all gases (at a given temper ature) contain the same number of parti cles per unit volume. This is Avogadro’s hypothesis, which he advanced in a paper published in 1811. He was careful to specify that the particles need not be individual atoms, but might be combina tions of atoms (which we now call mole cules, a word Avogadro coined). Avoga dro was the first to distinguish between atoms and molecules in this way. On this basis he could easily explain Gay-Lussac’s law of combining volumes. Furthermore, when water was electro lyzed and the hydrogen and oxygen col lected separately, as Ritter [413] had first done a decade earlier, the volume of hy drogen produced was twice the volume of oxygen. Avogadro could then use his hypothesis to maintain that the water molecule contained two hydrogen atoms for each one of oxygen. Then, if the ox ygen as a whole weighed eight times as much as the hydrogen, the individual ox ygen atom was sixteen times as heavy as the individual hydrogen atom (not eight times, as Dalton [389] insisted). But Avogadro’s suggestion, loudly and repeatedly proclaimed by him, was little regarded in the following decades. Ampère [407] was one of the few who upheld it but Dalton rejected it with vigor and Berzelius [425], the most prominent chemist of his time, ignored it. Partly this was because Avogadro did not support it with a convincing body of experimental evidence. The result was that there was great and continuing confusion in differentiat ing atoms from molecules, and atomic weights from molecular weights. It was not until Avogadro’s countryman Can nizzaro [668] took up the cudgels on his behalf (half a century after the hypothe sis was published and, alas, shortly after Avogadro’s death) that the hypothesis finally took its rightful place. Now, of course, Avogadro is famous. His name is applied to the number of atoms or molecules present in an amount of substance that has a mass of its atomic (or molecular) weight in grams. Thus carbon dioxide has a molecular weight of 44. Forty-four grams of car 277 [413] RITTER
COURTOIS [414] bon dioxide contains “Avogadro’s num ber” of molecules, and in Arabic fig ures that number comes out to 602,600,000,000,000,000,000,000. [413] RITTER, Johann Wilhelm German physicist
now, Poland), December 16, 1776 Died: Munich, Bavaria, January 23, 1810 Initial advances in current electricity moved quickly. In early 1800 Volta [337] had constructed the first battery, and within months Nicholson [361] had used the electric current to break up water into hydrogen and oxygen. Within months after that, still in 1800, Ritter, the son of a minister and an apothecary by profession, who had stud ied at the University of Jena and taught there as well, was able to repeat Nichol son’s experiment with electrodes placed in such a way that the hydrogen and ox ygen produced from the water could be collected separately. He also announced that if a current was passed through a solution of copper sulfate, metallic cop per could be made to plate out. This was the beginning of electroplating. Ritter at tempted to use his experiments to revive the dying phlogiston theory, which had been mortally wounded by Lavoisier [334], and he failed, of course. Ritter made a startling advance in con nection with light in 1801. It was well known that silver chloride broke down in the presence of light, liberating finely divided metallic silver, the presence of which turned the originally white silver chloride black. (This is the key chemical reaction involved in photography.) Rit ter found, as Scheele [329] had reported a generation earlier, that the blue end of the spectrum was far more efficient in bringing this about than the red end was. He went on to discover, however, to his amazement, that the region beyond the violet end, where nothing was present to the eye, was more efficient in this respect than any visible region of this spectrum. Like Herschel [321] the year before, Rit ter was forced to conclude that radiation existed that was invisible to the eye. The section of the spectrum immediately ad jacent to the violet end is now called ul traviolet (“beyond the violet”) radiation. Because of its action on silver chloride, it was sometimes referred to as chemical rays. Toward the end of his short life, Ritter grew interested in dowsing and other mystical practices. Nothing came of it, of course. [414] COURTOIS, Bernard (koor-twahO French chemist
8, 1777
Died: Paris, September 27, 1838 Courtois’s father had once served as assistant to Guyton de Morveau [319] at Dijon University and was a manufac turer of saltpeter (potassium nitrate), a compound of importance in the manu facture of gunpowder. Courtois assisted him in the factory and served an appren ticeship to an apothecary. He was admit ted, with Guyton de Morveau’s recom mendation, to the École Polytechnique, where he studied under Fourcroy [366] and Thénard [416], After a period in the army as a phar macist, Courtois returned to the saltpeter business. His father had done poorly, but Courtois kept doggedly at the job, partic ularly since France (now revolutionary) was at war and needed saltpeter badly. Courtois had, in his early researches, isolated morphine from opium extract. It was the first alkaloid to be obtained in pure form. He is better known, however, for another discovery, which came about as follows. The method of manufacturing potas sium nitrate in those days used potas sium carbonate (potash) as one of the starting materials. To get the potassium carbonate, it was Courtois’s practice to burn seaweed. The ash contained the potassium carbonate and, of course, a number of other things as well. There were sulfur compounds, for instance, which were undesirable and which Cour tois got rid of by heating in acid. One day in 1811 he added too much 2 7 8
[415] GAUSS
GAUSS [415] acid and on heating obtained a beautiful violet vapor. On condensing, it produced dark, lustrous crystals. He investigated the new substance but conscious (or per haps overconscious) of his own short comings as a chemist passed it on to others. By 1814 Davy [421], who was shown the new material on the occasion of his tour of Europe, and Gay-Lussac [420] had shown it to be a new element and Davy suggested the name iodine, from the Greek word for violet. Seaweed still remains one of the prime sources of iodine. The discovery gave Courtois a mea sure of fame and in 1831 he received a prize of 6,000 francs from the Academy of Sciences. However, he had no better luck in business than his father. The salt peter factory failed when the Napoleonic Wars ended and the need for gunpowder abated. He eked out a living, but not much of one, by preparing and selling iodine; and in the end, died in poverty. [415] GAUSS, Johann Karl Friedrich (gowss) German mathematician Born: Braunschweig (Brunswick, in English), April 30, 1777 Died: Gottingen, Hannover, Feb ruary 23, 1855 Gauss, the son of a gardener and a servant girl, had no relative of more than normal intelligence apparently, but he was an infant prodigy in mathematics who remained a prodigy all his life. He was capable of great feats of memory and of mental calculation. There are those with this ability who are of only average or below-average mentality, but Gauss was clearly a genius. At the age of three, he was already correcting his fa ther’s sums, and all his life he kept all sorts of numerical records, even useless ones such as the length of lives of fa mous men, in days. He was virtually mad over numbers. Some people consider him to have been one of the three great mathe maticians of all time, the others being Archimedes [47] and Newton [231]. His unusual mind was recognized and he was educated at the expense of Duke Fer dinand of Brunswick. In 1795 Gauss en tered the University of Gottingen and in 1799 received his doctor’s degree in ab sentia.
While still in his teens he made a num ber of remarkable discoveries, including the method of least squares, advancing the work of Legendre [358] in this area. By this the best equation for a curve fitting a group of observations can be made. Personal error is minimized. It was work such as this that enabled Gauss, while still in his early twenties, to calculate an orbit for Ceres from Piazzi’s [341] few observations so that the first asteroid might be located once more after it had been lost. (The 1001st as teroid discovered was named Gaussia in his honor.) He also worked out theories of perturbations that were eventually used by Leverrier [564] and John C. Adams [615] in their discovery of the planet Neptune. While still in the university he also demonstrated a method for constructing an equilateral polygon of seventeen sides (a 17-gon) using only straightedge and compass. Here was a construction all the ancient Greeks had missed. Gauss went further: he showed that only polygons of certain numbers of sides could be con structed with straightedge and compass alone. (These two tools were the only ones thought suitable for geometric con structions by Plato [24].) A polygon with seven sides (a “heptagon”) could not be constructed in this fashion. This was the first case of a geometric con struction being proved impossible. From this point on, the proof of the impossible in mathematics grew in importance, reaching a climax with Godel [1301] nearly a century and a half later. Gauss was quickly recognized as the greatest mathematician of his time, even by Laplace [347] who was not likely to be overgenerous in his estimate of others. (For that matter, Gauss in later life was not overgenerous to younger mathematicians either. The case of Niels Abel [527] is an example.) Gauss did important work on the theory of numbers, the branch of mathe matics that Fermat [188] had founded, 279 [415] GAUSS
THÉNARD [416] and on every other branch of mathe matics. He also worked out a non Euclidean geometry—a geometry based on axioms different from those of Euclid [40]—but hesitated to publish, for he had the habit, in any case, of keeping some of his results secret for periods of time. Lobachevski [484] and Bolyai [530] published first and obtained the credit. In 1799 Gauss proved the funda mental theorem of algebra, that every al gebraic equation has a root of the form a -f bi, where a and b are real numbers and / is the square root of minus one. Numbers of the form a -f bi are called complex numbers, and Gauss showed that these can be represented as analo gous to the points on a plane. This was the work that earned for him his doctor ate. In 1801 he went on to prove the fundamental theorem of arithmetic: that every natural number can be represented as the product of primes in one and only one way.
All this was not without a price, for his intense concentration on the great work that poured from him withdrew him sometimes from contact with hu manity. There is a story that when he was told, in 1807, that his wife was dying, he looked up from the problem that engaged him and muttered, “Tell her to wait a moment till I’m through.” Outside the realm of pure mathematics it was his work on Ceres that gained Gauss fame. In 1806 Gauss’s sponsor, Ferdinand of Brunswick, was dead, fighting against Napoleon, and Gauss had to have some way of making a liv ing. Through the influence of Humboldt [397], a great admirer of Gauss, and the mathematician’s own record in connec tion with Ceres, he was appointed direc tor of the Gottingen Observatory in 1807. Even then, war conditions kept him on a bare subsistence level for some years. During his years at Gottingen, Gauss devised a heliotrope, an instrument that reflected sunlight over long distances, so that light rays could be put to work as straight lines marking the face of the earth, and more precise trigonometric determinations of the planet’s shape could be made. He worked also on terrestrial magne tism and instituted the first observatory designed specifically for work in that field. He calculated the location of the magnetic poles from geomagnetic obser vations and his calculations proved re markably accurate. In 1832 he devised a logical set of units of measurement for magnetic phenomena. The unit of mag netic flux density was eventually named the gauss. He pointed out that once a few fundamental units were established (as, for instance, those for length, mass, and time) many other derived units (such as those for volume, density, en ergy, viscosity, power, and so on) could be expressed in terms of those funda mental units. In 1833 he even con structed an electric telegraph, as Henry [503] was doing in the United States. His agile mind never seemed to cease. At the age of sixty-two he taught himself Rus sian.
He remained on the faculty at Gottin gen all his working life but hated teach ing and had few students. Each of his two wives died young and only one of his six children survived him. His life was filled with personal tragedy, and though he died wealthy, he also died em bittered. After his death, a medal was struck in his honor by the king of Hannover. A statue of him, raised by the city of his birth, stands on a pedestal in the shape of a 17-pointed star, celebrating his dis covery of the construction of the 17-gon. [416] THÉNARD, Louis Jacques (tay- nahrO
French chemist Bom: La Louptière, Aube, May 4, 1777
Died: Paris, June 21, 1857 Thénard’s was a true rags-to-riches story. He was the son of a poor peasant who, in the best tradition of such things, struggled hard to obtain an education for his son. Thénard went to Paris and stud ied chemistry for three years under con-
[417] OERSTED
OERSTED [417] ditions of semistarvation until he was befriended by Vauquelin [379], who, himself the son of a peasant, had not forgotten his own early life. Thénard eventually grew well-to-do by responding to a demand by Chaptal [368] for the development of a color as bright as ultramarine but capable of withstanding the heat of furnaces used in preparing porcelain. Thénard obliged with what is now known as “Thénard’s blue” (which contains an aluminum- cobalt oxide). Thénard’s greatest fame came in his collaboration with his lifelong friend Gay-Lussac [420], but he also did much on his own. In 1818 he discovered hy drogen peroxide and between 1813 and 1816 he published an important four- volume text on chemistry. He was made a baron in 1832 by Charles X, after having become a member of the Chamber of Deputies in 1828 (thus pointing the way in which his collaborator, Gay-Lussac, was to fol low in the next reign). Eight years after Thénard’s death, his native village was renamed La Loup- tière-Thénard. [417] OERSTED, Hans Christian (eri sted)
Danish physicist Bom: Rudkøbing, Langeland, August 14, 1777 Died: Copenhagen, March 9, 1851 The young Hans worked in his father’s apothecary shop, but this early training, which in most cases would have led straight to a career in chemistry, led to physics instead. He studied at the Uni versity of Copenhagen, where he ob tained his Ph.D. in 1799 for a disser tation on Kant’s [293] philosophy. He then traveled through Europe, and in 1806 was appointed professor of physics and chemistry at his alma mater. He be came an ardent adherent of the school of “nature philosophy” of which Oken [423] was an outstanding member. He accepted, with great gullibility, foolish theories and faked experimental work by men he admired and for a while his scientific reputation lay under a cloud. His brother Anders, younger by a year and a half, took to law, became attorney general of Denmark, and eventually the prime minister. He was a very unpopular prime minister and underwent impeach ment proceedings after a forced resigna tion. It would seem, then, thanks to a single experiment, that Hans Oersted had taken the better road to fame. It was in 1819 that Hans Oersted’s great day came. He too was experi menting with the electric current, as half of Europe’s scholars were doing. As part of a classroom demonstration, he brought a compass needle near a wire through which a current was passing. Scientists had long suspected there might be some connection between electricity and magnetism and Oersted may have felt that the current in the wire might have some effect on the needle. It did indeed. The compass needle twitched and pointed neither with the current nor against it, but in a direction at right angles to it. When he reversed the direction of the current, the compass needle veered and pointed in the oppo site direction, but still at right angles. The astounded Oersted remained after class to repeat and continue his experi ments.
This was the first demonstration of a connection between electricity and mag netism, and Oersted’s experiment may be considered the foundation of the new study of electromagnetism. Oersted’s discovery (published in Latin, in the old-fashioned way) was an nounced in 1820, and it set off an explo sion of activity. Coulomb [318] had de veloped views indicating that electricity and magnetism could not interact, and he had been very persuasive; but now it was clearly seen that he had been wrong. Arago [446] and Ampère [407] charged into the fray. Later, in the hands of Faraday [474] and Henry [503] espe cially, electromagnetism was to grow into an entity that was eventually to change the world as drastically as the steam engine had changed the world a century before and as the internal com
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