Migration of Scientists and the Discovery of Metals
The movement of scientists played an important role in the discovery, isolation and industrialization of a number of metals.
In 1735, Spanish mathematician and naval officer Antonio de Ulloa (1716-1795) accompanied the expedition sent from France by Louis XV to measure the Arc of the Meridian at the equator. In his account of the voyage, the multi-volume work Relacion Historica del Viaje à la America Meridional (published in Madrid in 1748), he mentioned that in the alluvial gold mines of El Chocó in New Granada (now Colombia), between the Andes and the Pacific Ocean, there was an unworkable metallic stone that looked like silver, but was not silver. It was called platina, a diminutive of plata, the Spanish word for silver. De Ulloa also mentioned that it made gold ores useless if it was associated with them in large proportions, apparently because they did not respond to amalgamation. He sent copies of his report to the Royal Society in London.
Around 1741, William Brownrigg (1711-1800), a medical doctor in Whitehaven, England, received a specimen of native platina from his friend Charles Wood (1702-1774), a metallurgist in the mint in Jamaica who had obtained it from Cartagena in New Granada. Together with William Watson (1715-1787), a British physician and naturalist, he prepared an accurate description of the metal and its properties and presented specimens to the Royal Society in London in 1750. Other specimens of this curious new substance, “which it has hitherto not been possible to melt by fire or by any of the Spanish arts,” found their way to Europe from Spanish America and were examined by notable chemists of the period.
However, what was not fully realized until almost 200 years later was that a native industry, well aware of the separate identity of platinum and skilled enough to work it into jewelry and other decorative forms, had flourished in those parts of South America many centuries before. The native Indians had successfully mixed tiny grains of gold and platinum together by heating; then, by careful hammering, they had been able to produce a sound homogeneous mixture of the two metals.
Much work was going on in England, France, Prussia, Spain and Sweden. Torbern Bergman (1735-1784), a professor of chemistry at Uppsala University in Sweden, proposed the name “platinum” in 1777, in line with the nomenclature using the Latin ending “um,” which he had adopted for several other metals and which is universal today. Bergman, too, finally confirmed that platinum was a new metal.
When the Basque Society of Friends of the Country, the first scientific society in Spain, received a large quantity of platinum from New Granada, French chemist Pierre François Chabaneau (1754-1842), who was teaching at the Vergara Seminary founded by the society, succeeded in 1783 in producing malleable platinum by hammering a platinum sponge while white hot. The director of the Royal Laboratory of Natural History in Madrid then asked the Spanish authorities to send a large batch of the native grains for use by Joseph Louis Proust (1754-1826), another French chemist working in his laboratory. Proust was the first to report that a residue was obtained that was insoluble in aqua regia. However, he failed to realize that this residue contained other new metals, which were later discovered by other chemists.
Naturally occurring alum-stone used by alchemists to enhance the dyeing of textile fibers was known to yield a white “earth” when heated at high temperature. This white earth was known as alumina and was an exceptionally stable material; it was considered to be a chemical element like gold, copper and tin. In 1801 in northern Italy, when Alessandro Volta discovered that an electric current was generated when two metals were separated by an electrolyte, chemists in Europe immediately started to study this new phenomenon and tried to make use of it. In 1801 Napoleon Bonaparte, as First Consul, invited Volta to Paris to give a demonstration of the principle of his discovery at the French National Institute (the body that replaced the French Academy during the revolutionary period).
Napoleon was impressed and awarded Volta the Gold Medal of the Institute, ordering funds to be given to the École Polytechnique to build a large battery for research.
The news of Volta’s discovery rapidly reached England and a very large battery, similar to the one constructed in Paris, was built at the new Royal Institution in London, where in 1807, Humphry Davy succeeded in isolating potassium and, a few days later, sodium, using this battery. Once these two reactive metals were available, they became the focus of intensive study. Their vigorous reaction with water and their spontaneous burning in air was very impressive. In 1808, Davy announced his belief that the plentiful compound alumina was the earth (oxide) of an undiscovered metal. From then on, scientists were making efforts to obtain this new metal.
A Visitor to Copenhagen
Davy never made any aluminum himself; however, in the early 1820s, Danish scientist Hans Christian Oersted (1777-1851) succeeded in producing a tiny sample of the metal in a laboratory by reducing the aluminum chloride with potassium amalgam. He had prepared aluminum chloride a few years earlier for the first time by heating a mixture of alumina and charcoal in a stream of chlorine. Chlorine, at that time, was a laboratory curiosity, isolated a few years earlier by Carl Wilhelm Scheele.
On his return trip from Stockhom after completing his studies under Jöns Jacob Berzelius, Friedrich Wöhler (1800-1882) stopped in Copenhagen in 1824 to visit the university. He met Oersted and learned about his experiments to isolate aluminum.
Back in his laboratory in Berlin in 1827, he successfully repeated Oersted’s experiment. In 1836, he accepted a professorship position at the university and moved to Göttingen. In 1845, he succeeded in making aluminum in slightly larger amounts from which he was able to show that aluminum was a light metal. Wöhler devoted his later work to organic chemistry and became known for his synthesis of urea from ammonium cyanate, a reaction that defeated the concept of “vital force” that stated organic compounds could only be produced by living organism.
Aluminum Production in France
French chemists were also actively researching how to produce aluminum. Henri Sainte-Claire Deville (1818-1881), professor of chemistry at the École Normale in Paris, already produced aluminum in 1854 by electrolyzing a molten aluminum chloride-sodium chloride mixture. However, this route was abandoned because, at that time, electric current needed for electrolysis was obtained only from batteries, which were tedious to construct, operate and maintain. He therefore considered the chemical method devised by Wöhler and developed the process on a commercial scale. However, the process was expensive.
A Visitor from America
Frank Fanning Jewett (1844-1926), who had received his undergraduate and graduate education in chemistry and mineralogy at Yale University, spent two more years (1873 to 1875) at the University of Göttingen with Wöhler where he learned about the promise of the new metal. Jewett returned home to become an assistant at Harvard University. He was soon nominated to teach at the Imperial University in Tokyo, Japan, where from 1876 to 1880, he was one of the small groups of westerners who initiated the teaching of science at the university. In 1880, he became a professor of chemistry and mineralogy at Oberlin College in Ohio. When Charles Martin Hall (1863-1914) took his chemistry course at Oberlin, he heard Jewett lecture on aluminum, display his sample of the metal and predict the fortune that awaited the person who could win this metal from its ore. Under Professor Jewett’s guidance and encouragement, Hall worked on aluminum chemistry in Jewett’s laboratory and at home until he succeeded in 1886 in producing the first ingot of aluminum by electrolyzing alumina dissolved in molten cryolite; a process was discovered simultaneously and independently by Paul Louis Heroult (1863-1914) in France and is the same process used today.
The rare earths are a group of 14 elements occurring together in a number of minerals, the most important being monazite, xenotime and bastnasite. It took nearly 200 years until all members were individually separated. Their close similarity caused considerable confusion and problems during their discovery. The first phase of separation was due to Swedish chemist Carl Gustav Mosander (1797-1858), a student and later a co-worker of Berzelius, who based the separation on the colour of ions in solution and on the salts, crystal form and reactivity. This was not enough to overcome the difficulties involved; new methods of analysis were necessary. The movement of chemists between different laboratories played a key role in this effort.
Spectroscopic analysis was discovered in Heidelberg, Germany, in 1859 by Gustav Kirchhoff (1824-1887), a physics professor, and Robert Bunsen (1811-1899), a chemistry professor. The method proved to be so successful that immediately after putting it into use, the discoverers were able to find two new elements — rubidium and cesium. Students visited Bunsen from all over Europe to learn this technique and chemists brought samples there to be analyzed.1
Two students who came to Bunsen — Jons Fridrik Bahr from Uppsala (1815-1875) and Carl Auer (1858-1929) from Vienna — played a particular role in the history of the rare earths. Bahr brought with him samples of rare earth minerals for analysis by Bunsen’s spectroscope. He also worked in his laboratory for a short time and developed a method of separation based on the selective decomposition of the nitrates. Bunsen later asked Auer to study different spectra of rare earths extracted from gadolinite. Auer noted that certain lines disappeared during chemical purification; thus, he could know when an element had reached its highest degree of purity.
On his return to Vienna, Carl Auer took samples of rare earth minerals with him, set up a spectroscopic laboratory and studied the earths from gadolinite. He introduced fractional crystallization of the ammonium double nitrates to study the separation of the rare earths. Within two years, he was able to report that didymium (the twin of lanthanum) was in fact two elements, which he called neodymium (the new didymium) and praseodymium (the green didymium in reference to the colour of its salts). He used his new method of fractional crystallization using a seven-kilogram batch of cerite. This work resulted in the accumulation of a large amount of pure lanthanum salts that later played an important role in his research on incandescence.
As early as 1826, it was known that CaO pastilles produced light when heated in the oxyhydrogen flame. Later, zirconium oxide was used. Auer found that adding some lanthanum oxide to ZrO2 improved the incandescence. He had on hand a considerable quantity of lanthanum salts derived from the didymium splitting. At night, he lit his laboratory window with the new light he generated, attracting the attention of passers-by. For this purpose, he invented the gas mantle — a stocking made of cotton thread soaked in a solution of the earth metal salts. After the organic matter was burned off, a skeleton of the metal oxide was left. This emitted light when heated in a laboratory Bunsen burner. In 1887, he opened a factory in Atzgersdorf, a suburb of Vienna, to prepare the rare earth salts necessary for the soaking solution and to sell it to customers in Germany, England and the United States. This was the beginning of the rare earths industry.
Juan Jose D’Elhuyar y de Zubice (1754-1796) and his brother, Fausto D’Elhuyar y de Zubice (1755-1833) were two of the most travelled metallurgists of their time. This activity resulted in distinguished contributions to science, education and industry. They were born in Logroño in northern Spain, to a well-to-do Basque family. Their father was the town surgeon. In 1778, Juan Jose was sent to study metallurgy at the School of Mines in Freiberg, at the expense of the Basque Society. From December 1781 to July 1782, he went to Uppsala in Sweden to study under Torbern Bergman, the famous Swedish chemist. There he worked on tungstic acid that Carl Wilhelm Scheele had separated from the mineral known at that time as tungsten (in Swedish, this means “the heavy stone”; this mineral is known today as scheelite). On his return to Spain, he was appointed professor of metallurgy at the Seminario in Vergara.
Fausto also went to France and Freiberg to study chemistry and metallurgy with his brother. Upon his return in 1781, he was also appointed as a professor at the Seminario in Vergara. In 1783, the two brothers worked together on the analysis of a specimen of wolframite from a tin mine in Zinnwald, Germany, and separated from it an insoluble yellow powder which they called wolframic acid. They showed it to be identical to tungstic acid, separated earlier by Scheele.
The possibility of obtaining a new metal by reducing tungstic acid had already been suggested by Bergman and Scheele. The D’Elhuyar brothers heated an intimate mixture of tungstic acid with powdered charcoal in a sealed crucible. After cooling, they found a dark brown metallic button, which crumbled easily in their fingers, and when they examined the powder with a lens they saw metallic globules of tungsten. They published the result of their work in the journal of the society.
In 1786, Juan José was sent to Bogotá in New Granada (now Colombia) to develop the mines there, while his brother Fausto was sent to Schemnitz (now Banska Stiavnice in the Slovak Republic) and Vienna to study the new method of amalgamation developed by Ignaz von Born.
Juan José got married in 1788 and had three children. In the struggle for independence from Spain in 1811, he sympathized with his brother-in-law, who supported independence. When the latter came into disgrace, he was put under house arrest. He died at the young age of 42. His son Luciano, at the age of 19, was sent on an expedition for the liberation of Venezuela in 1813. He died at the age of 22. Fausto married a German girl and in 1788, was sent to New Spain to be director general of mines. While in Mexico he published a book on the making of coins in New Spain. He was then commissioned to establish a school of mines, which was planned by Joaquin de Velázquez Cardenas y León, who died before his plan was realized. Fausto became its first director when it was opened in 1792 and stayed there for more than 30 years until the outbreak of the War on Independence; he returned to Spain in 1821. There he was made director general of mines and planned the School of Mines of Madrid. In 1818, he wrote a treatiseon The Influence of Mining in New Spain.
Alexander von Humboldt (1769-1859), a graduate of the Mining Academy in Freiberg, made extensive voyages to South America, Mexico, Europe and Central Asia, and wrote his Voyages in multiple volumes (1805-1834). His books contributed to modern natural science. One of his trips contributed to establishing the validity of the discovery of vanadium. On his way from Acapulco to Vera Cruz in 1803, Humboldt stopped at Mexico City to visit Manuel del Rio (1764-1840), his friend and schoolmate from the Freiberg Academy. There he learned about del Rio’s discovery of a new element in a lead mineral from Zimapan in 1801, which he had called erythronium because of the red colour that its salts acquired when heated. However, del Rio was not sure that he made a new discovery because there was an earlier report published in 1797 by French chemist Nicholas Louis Vauquelin announcing the discovery of a new metal, which he called chromium. Del Rio thought that he had made a mistake and his erythronium might have actually been a chromium compound.
Humboldt carried a sample of this mineral with him and, on his return to Germany, gave it to Friedrich Wöhler, then professor of chemistry in Berlin. When Wöhler analyzed this mineral in 1831, he proved that it contained the metal vanadium, recently discovered by his colleague in Stockholm, Swedish chemist Nils Gabriel Sefström (1787-1854). Wöhler then proved that erythronium and vanadium were one and the same. Thus, del Rio was right in his discovery. The mineral from Zimapan is now known as vanadinite — PbCl2•3Pb3(VO4)2.