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301 [448] CHEVREUL
CHARPENTIER [449] struction of the Eiffel Tower when he was a centenarian. (Both his father and mother had lived to be over ninety, which shows the value of carefully choosing one’s parents.) In 1803 he went to Paris to study under Vauquelin [379] and Fourcroy [366], and his first investigations were upon indigo. On Vauquelin’s death, Chevreul succeeded to his post at the Jardin des Plantes. His chief fame, how ever, rests upon his studies of the chemi cal nature of fats, which branch of chemistry he initiated. In 1809 he was set to working on soap (which is or dinarily produced from fat). He treated this with hydrochloric acid and found that insoluble organic acids rose to the top of the watery solution. He isolated stearic acid, palmitic acid, and oleic acid, the three most common and important constituents of fats and oils. He also showed that spermaceti so treated did not behave similarly and was a wax rather than a fat. In 1825 Chevreul, along with Gay- Lussac [420], took out a patent on the manufacture of candles from these fatty acids. In our own days, when candles are little more than curiosities, the impor tance of the Chevreul-Gay-Lussac ad vance is easy to miss. However, the fatty acid candles were harder than the old tallow candles, gave a brighter light, looked better, needed less care while burning, and didn’t smell as bad. To the men of the mid-nineteenth century, the improvement was a major one and the next year Chevreul was elected to the Academy of Sciences. Fats were not Chevreul’s only concern, however. In 1815 he isolated sugar from the urine of a diabetic and showed that it was identical with grape sugar (glu cose). This was the first step in the di rection of recognizing diabetes as a dis ease of sugar metabolism, but a century remained before Banting [1152] and Best [1218] were to place the finishing touch on this line of research. Chevreul was a pioneer in the analysis of organic substances, writing a book on the subject in 1824. Shortly after, he be came director of dyeing at a famous tap estry establishment and grew interested in the psychology of color. He tried to establish reasonable standards in the field and ended by strongly influencing the Impressionist school of painting. In the 1850s he worked to expose fakery in spiritualism, which was then quite a popular fad, having ensnared Hare [428] in the United States, for in stance. He was a pioneer in gerontology, a study for which he was peculiarly qual ified, and in his nineties studied the psychological effects of old age. His hun dredth birthday was celebrated by the chemical world with terrific enthusiasm, including a torchlight parade through the streets of Paris; and he remained a lively participant in chemical affairs to the end, publishing his last scientific paper at the age of 102. He was one of those fortunates who live into extreme old age without ever living long enough to retire, and his fu neral at the Cathedral of Notre Dame was attended by thousands. [449] CHARPENTIER, Johann von (shahr-pahn-tyay') German-Swiss geologist Born: Freiberg, Saxony, Decem ber 7, 1786 Died: Bex, Vaud, Switzerland, September 12, 1855 Charpentier was the son of a mining engineer, and followed his father’s pro fession. He entered the Mining Academy at Freiberg and studied under Werner [355], He did excellent work in copper mines in the Pyrénées and salt mines in western Switzerland, but it was not in mining that he did his most significant service to science. In 1818 a glacier dammed a lake, which eventually broke through and drowned many people. That turned his attention to glaciers. A friend of his, Venetz [453], believed that glaciers had at one time been more extensive than at present, but Charpentier at first refused to believe that. Upon studying the Alpine regions closely, however, he was as tonished to find that the evidence seemed to support that seemingly wild notion. 3 0 2
[450] FRAUNHOFER FRAUNHOFER
He found that there were boulders strewn where the geologic evidence showed they had no business being, and it seemed possible they had been brought there by glaciers that now no longer existed. He wasn’t quite sure how the glaciers had formed in the first place; how they moved; why they disappeared. However, a younger naturalist, Louis Agassiz [551] visited Charpentier and was convinced by the latter’s arguments against his ini tial skepticism, and it was he who car ried the matter to a satisfactory conclu sion.
[450] FRAUNHOFER, Joseph von (frownTioh-fer) German physicist and optician
1787
Died: Munich, June 7, 1826 Fraunhofer, the eleventh and youngest child of a glazier, was apprenticed to an optician in Munich, after having been left an orphan at eleven. Three years later, the rickety tenement he lived in collapsed, and he was the only survivor. The elector of Bavaria, Maximilian I, hearing of this, gave the now homeless orphan eighteen ducats out of pity. With this as capital, Fraunhofer launched him self on an optician’s career. He taught himself doggedly and went on to make glassworking into a fine art by studying the manner in which the properties of glass varied with the method of prepara tion. He made improvements in various optical instruments and ground prisms of excellent quality. His instruments helped Bessel [439] and Struve [483] determine stellar parallax. He was visited by Tsar Alexander I and by Gauss [415] when they were in search of instruments. He was interested in determining the refractive index of various types of glass since one of his specialties was the man ufacture of achromatic lenses, in which, thanks to the pioneering work of Dol- lond [273], glasses of different refractive index could be combined to eliminate spectrum formation. Naturally the re fractive indices of the glasses had to be known accurately if they were to be combined properly. In testing prisms of his glass for the purpose, Fraunhofer found in 1814 that the solar spectrum was crossed by nu merous dark lines. Even slight imper fections in the prism would have reduced the sharpness of the image sufficiently to fuzz out the lines, and that may perhaps explain the puzzling fact that Newton [231] had not observed them in his pio neering studies a century and a half be fore. Wollaston [388], twelve years earlier, had observed such lines, but where Wol laston had observed only seven, Fraun hofer detected nearly six hundred (and modem physicists can find ten thou sand). Fraunhofer went on to do more than observe. He measured the position of the more prominent lines, which he in dicated by the letters from A to K (let ters by which they are still known), de termining their wavelength, and showed that they always fell in the same portion of the spectrum, whether it was the di rect light of the sun that he studied or the reflected light from moon and planets. Eventually he mapped the posi tion of several hundreds of these lines, which are called Fraunhofer lines. He even went so far as to place a prism at the focal point of a telescope in order to pass the light of a star through it and he observed that the dark lines in its spectrum did not have quite the pat tern of those in sunlight. He had a great discovery in his grasp, but it eluded him. It eluded the world of science as well, for Fraunhofer’s reports on the subject were ignored and it remained for Kirchhoff [648] a half century later to forge of those lines a mighty instrument for chemists, physicists, and astronomers. Fraunhofer was the first to use grat ings (closely spaced thin wires) to serve as a refracting device that would form a spectrum out of white light. Since his time, much more delicate gratings (of fine, parallel scratches on glass or metal) have virtually replaced the prism for spectral purposes. Despite all his findings, scientific snob bery scorned him as a mere technician,
[451] SEFSTROM
PURKINJE [452] and though he might attend scientific meetings he was not allowed to address them.
He never married and he died of tu berculosis before he was forty. On his tombstone is engraved Approximavit si
so he did, as Kirchhoff was to demon strate by means even more remarkable than those of the great telescopes. [451] SEFSTROM, Nils Gabriel (seb/- strerm)
Swedish chemist Born: Ilsbo, Halsingland, June 2, 1787
Died: Stockholm, November 30, 1845
Sefstrom obtained his medical degree in 1813. Studying under Berzelius [425], he became fascinated by mineralogy, but first he practiced for four years as a phy sician. Then he accepted an appointment as professor of chemistry at a medical institute, and finally in 1820 he began to teach chemistry at a newly opened school of mines. At the school of mines, he became in terested in a process by which the man ager of an iron mine insisted he could tell whether a batch of iron was brittle or not. The iron was treated with hy drochloric acid, and the appearance of a black powder implied brittleness. Sefstrom investigated the process in 1831 and found that on some occasions iron was not brittle, though giving the same kind of powder. He examined and analyzed the powder and found a small quantity of metal that resembled ura nium or chromium and yet seemed to be neither. Closer study proved it to be a new metal, which he named vanadium after a Norse goddess. Eventually vanadium turned out to be identical to a metal reported by Del Rio [382] a generation earlier. Del Rio had called it erythronium, from the red color of some of its salts, but unfortunately he lacked confidence in his own discovery and let himself be talked out of consider ing it a new element. [452] PURKINJE, Jan Evangelista (poorTun-yay) Czech physiologist
(now in Czechoslovakia), Decem ber 17, 1787
In Purkinje’s lifetime, what is now Czechoslovakia was a part of the Aus trian Empire, with German the language of the ruling groups. Consequently, Pur kinje is usually known by this German version of his name. In Czech, however, it is Jan Evangelista Purkyne. Purkinje, the son of an estate man ager, was quietly studying for the priest hood when he felt a call to medicine. He made the necessary educational switch and obtained his medical degree in 1819. His Czech nationality stood in his way, but Goethe [349] approved of Purkinje’s thesis on vision, and he befriended him and used his influence to get him a post. Purkinje taught physiology at the Uni versity of Breslau in Germany from 1823 to 1850, and there, in 1839, he es tablished the world’s first independent department of physiology. He then taught at Charles University in Prague. He first described what is known as the Purkinje effect—that dim light appears bluer to the eye than it really is. He specialized in microscopy, making many improvements in technique. For instance, he was one of the first to use a mechanical microtome to prepare thin tissue slices for the microscope, instead of a simple razor wielded by a simple hand. (He was the first to give college courses in microscopy, doing so in the 1830s.) He was very aware of the cel lular makeup of skin and other animal organs (a type of makeup that some men at the time thought far more typical of plants than animals), but he stopped short of announcing a cell theory. That was left for Schleiden [538] and Schwann [563] a few years later. In Czechoslovakia, Purkinje is known as a poet (he translated the works of Goethe and Friedrich von Schiller) and as a vigorous Czech nationalist. To the rest of the world, however, his greatest
[453] VENETZ
FRESNEL [455] fame depends upon a single word, which he used partly because of his theological training. Adam, the first man, can be termed protoplast, for instance, because this comes from Greek words meaning “first formed” and in the Bible, Adam is described as just that. Purkinje, thinking of this, no doubt, referred in 1839 to the living embryonic material in the egg as the protoplasm. As far as the eventual animal was con cerned, this material was indeed the “first formed.” The word was next used by Mohl [542] in a slightly different sense, but eventually it came to mean quite generally the living material within the cell. [453] VENETZ, Ignatz (veil-nets') Swiss geologist Born: Visperterminen, Valais, March 21, 1788 Died: Saxon-les-Bains, Valais, April 20, 1859 Venetz was the son of a poor carpen ter, who was intended by his parents for the priesthood, but he evaded that and studied science and mathematics instead. He became chief engineer of Valais when Switzerland was part of the Napo leonic Empire, but he was unable to avert disaster when a glacier dammed a lake. He knew the glacier was bound to thaw and release the dammed water; but his effort to allow the water to leak away in controlled fashion failed, and the flood that followed inundated a valley and destroyed life and property. It turned his attention to glaciers, and he found that typical striations left in rock by glaciers extended for many miles beyond the limits of glaciers. This made him think that glaciers had in the past covered far more territory than they did now. He published these thoughts of his in 1821, but they were generally ignored. However, his friend Charpentier [449] was convinced and made additional ob servations of his own (always careful to preserve Venetz’s priority). These were also ignored but served to convert Agas siz [551], [454] PELLETIER, Pierre Joseph (pel- tyay')
French chemist Born: Paris, March 22, 1788 Died: Paris, July 19, 1842 Pelletier, who came of a family of apothecaries, earned his doctorate at the Paris School of Pharmacy in 1812. In 1815 he was given a professorial ap pointment at the school and by 1832 was its assistant director. Few can have had the opportunity to discover so many pharmaceutically in teresting natural products. In 1820 with another chemist, Caven- tou [493], he isolated such alkaloids as brucine, cinchonine, quinine, and strych nine. These had powerful effects on the animal body, and Magendie [438] intro duced some of them into medical prac tice. This marked a shift in pharma cology from the use of infusions and ex tracts to that of known chemical entities, first of natural occurrence and later of synthetic ones (not necessarily known in nature).
Earlier, in 1817, Pelletier and Caven- tou had isolated a plant substance of no obvious value to medicine but of infi nitely greater value in the scheme of life. This was a green compound, the com pound in fact that makes plants green. They called it chlorophyll (from Greek words meaning “green leaf’). It super vised the chemical processes whereby green plants convert sunlight into chemi cal energy (photosynthesis), supporting thereby themselves and the entire animal kingdom, including man. [455] FRESNEL, Augustin Jean (fray- nel') French physicist Born: Broglie, Eure, Normandy, May 10, 1788 Died: Ville-d’Avray, near Paris, July 14, 1827 Fresnel was destined to complete Young’s [402] work on the wave theory of light, but, unlike Young, Fresnel, the son of an architect, was the very reverse 305 [455] FRESNEL
FRESNEL [455] of an infant prodigy. He was eight be fore he could read. Nevertheless his in telligence shone out with the passing years and he became a civil engineer, working for the government for most of his professional life. There was a short break in 1814, when Fresnel opposed the return of Napoleon from exile in Elba, was taken prisoner, and so lost his post. However, Napoleon’s return lasted only a hundred days and ended with Wa terloo; it was then Fresnel’s turn to re turn.
About 1814 Fresnel grew interested in the problem of light and independently conducted some of the experiments that Young had conducted a decade before. Arago [446] read Fresnel’s reports and was converted to the wave theory. He called Fresnel’s attention to Young’s work and Fresnel’s similar work was ac celerated. The Frenchman began to con struct a thorough mathematical basis for the wave theory. Huygens [215] had constructed part of such a mathematical basis a century and a half before, but Fresnel went beyond him. For one thing Huygens and all the wave theorists after his time (except for Hooke [223], whose freewheeling conjec tures hit the mark a number of times) had felt that light waves, if they existed, were longitudinal, with oscillations tak ing place along the line of propagation, as in sound waves. Young eventually suggested that light waves might be transverse, with oscillations at right an gles to the line of propagation, as in water waves. Fresnel adopted the trans verse wave view with alacrity and built up the necessary theoretical basis for it. The greatest victory of the transverse wave theory was the explanation of the phenomenon of double refraction through Iceland spar, discovered by Bartholin [210], Neither the particle theory nor the longitudinal wave theory could explain it. The transverse wave theory, however, could, and Fresnel showed that light could be refracted through two different angles because one ray would consist of waves oscillating in a particular plane, while the other ray consisted of waves oscillating in a plane perpendicular to the first plane. The two rays would therefore be expected to have different properties under certain condi tions and to be refracted differently by certain solids. Ordinary light, according to Fresnel’s views, consisted of waves oscillating equally in all possible planes at right an gles to the line of propagation, but light with oscillations unequally distributed among the planes was polarized light, a rather poor term introduced by Malus [408]. When the oscillations were re stricted to a single plane, as in the case of the light rays passing through Iceland spar, the light was said to be plane- polarized. Fresnel used his new view of light to design lenses for lighthouses, and they were more efficient than the mirrors they replaced. An understanding of polarized light, moreover, came to have an impor tant application to organic chemistry, through the work of Pasteur [642] a gen eration later. Arago, after a period of collaboration with Fresnel, backed out nervously when the transverse waves were adopted by the latter. Later he came round, but Fresnel had published his work alone and got credit alone. The difficulty that frightened Arago was this. If light consisted of waves, something must be waving. Early wave theorists postulated an “ether” filling space and all transparent substances. Light consisted of waves in this ether, which thus carried light even through an apparent vacuum and could be called a luminiferous (“light-carrying”) ether. (The word “ether” is taken from Aris totle’s [29] name for the fifth element that he considered to make up the heav ens.) If light waves were longitudinal the ether could be looked on as a very fine gaslike substance, indétectable to ordi nary instruments, and there would have been no difficulty in accepting that, or at least no more difficulty than there was in accepting Dalton’s [389] indétectable atoms. However, transverse waves can be transmitted through solids only, and if light waves were transverse, the ether would have to be viewed as a solid, and a very rigid one at that, considering the 3 0 6
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