Chemistry, Microscopy, and the Nanoworld

Scanning electron micrograph of table salt. Courtesy of www.semguy.com. Photo by Ric Felton.

By Cyrus C.M. Mody

In his 1915 textbook Elementary Chemical Microscopy Émile Monnin Chamot noted with dismay that “the American Chemist, usually ready to accept with alacrity all time, labor, and money saving devices, has been strangely backward in taking advantage of the benefits to be gained through the intelligent application of chemical microscopic methods in the industries and in research.”

For a fierce but brief period in the 17th century, chymists (alchemists and those natural philosophers with an interest in matter) had waxed enthusiastic about microscopy. Then, for nearly two centuries, chemists abandoned the microscope as a mere toy. Over time a few interdisciplinary entrepreneurs, such as Chamot, brought microscopy back into chemistry. But today Chamot would be proud: thanks to the instruments of nanotechnology, chemists have once again become ardent devotees of ultramicroscopy.

People have peered through quartz or glass to magnify objects since antiquity but, as with alchemy, the theory of lens making crossed to medieval Europe from the Arab world. By the 14th century Western Europeans had figured out how to grind lenses for spectacles; two centuries later the Dutch had learned to combine multiple lenses, resulting in the telescope and the microscope. When those inventions reached Italy in the 1620s, natural philosophers “swarmed” to the microscope to draw loving portraits of giant, magnified bees, the family symbol of Pope Urban VIII.

Outside bee-mad Italy, microscopes did not catch on until the 1660s. Heightened interest flowed from new ideas about life and matter, ideas that also fed the chemical evolution. One was the “mechanical” philosophy, which held that all matter—even living things—could be analyzed using the mechanical laws of Galileo, Descartes, and Newton. The other was the theory of corpuscles, according to which the world is made up of small particles whose size, shape, and motion determine material properties. Microscopy promised to shed light on the validity and relation of these theories.

Some microscopists thought that corpuscles would soon be made visible. Henry Power, for example, proposed in the preface to his 1664 book Experimental Philosophy: “If the Dioptricks further prevail . . . we might hope, ere long, to see the Magnetical Effluviums of the Loadstone, the Solary Atoms of light, . . . the springy particles of Air, the constant and tumultuary motion of the Atoms of all fluid Bodies, and those infinite, insensible Corpuscles.” The microscope helped forge “chymistry” from alchemy; by applying the systematic methods of the new empiricism to microscopy, natural philosophers hoped that the hidden, invisible (or occult) properties of matter described by alchemists might finally be revealed. Indeed, the most celebrated early microscopical publication, Robert Hooke’s Micrographia, which was published in 1665, is a paean to the new world revealed by the empirical methods of the Royal Society.

Microscopy’s Decline and Rise

By 1700, though, it was becoming clear that microscopes made with hand-ground lenses would not reveal the corpuscular nature of matter any time soon. Chymists despaired of answering fundamental philosophical questions about matter with a microscope and turned to the indirect characterization techniques on which modern chemistry was built. As Hooke put it in his 1692 book Philosophical Experiments and Observations, microscopes “are now reduced almost to a single Votary, which is Mr. [Antoni van] Leeuwenhoek; besides whom, I hear of none that make any other Use of that Instrument, but for Diversion and Pastime” (p. 261). Leeuwenhoek himself used the microscope to observe the physical structure of living things rather than to look for the elusive chemical corpuscles. His intellectual heirs were anatomists, not chemical pioneers like Priestley and Lavoisier. Still, chemists, including Priestley himself, like most scientific amateurs and salonnières, often owned a microscope as an expensive but fashionable toy.

By the 19th century anatomy and chemistry were becoming distinct disciplines, with the microscope as a point of contact. Technological improvements—particularly the achromatic lens in the 1820s—combined with such cultural shifts as the rise of Romanticism gave biological microscopists added authority. These newly confident microscopists had a complicated relationship with chemistry. In part the two communities were rivals for knowledge of the subvisible world. By 1837, for example, Theodor Schwann (founder of the cell theory) and other biologists were using microscopy to argue, persuasively, that yeast was composed of living organisms whose metabolism is responsible for fermenting sugar into alcohol. Eminent chemical authorities—Justus von Liebig, Jöns Jakob Berzelius, and Friedrich Wöhler—attacked Schwann and proclaimed yeast to be a nonliving precipitate. Liebig and Wöhler had only recently synthesized urea, undermining the romantic concept of “vitalism” (that organic chemicals have properties endowed by some mysterious force deriving from living beings). These pioneering organic chemists’ somewhat misplaced opposition to Schwann may have arisen from fears that Schwann’s insistence on living yeast’s role in fermentation marked a return to vitalism.

Still, chemistry, especially through its dyes and stains, offered remarkable tools in making the microscopic world observable. By the 1850s histologists developed a variety of arcane ways to harden, fix, and preserve their specimens using materials like Canada balsam (a resin of the balsam fir). For staining they depended on carmin, a chemical derived from cochineal, a red dye made by grinding females of the cochineal beetle, a parasite of the prickly pear cactus in Mexico. But William Perkin’s synthesis of mauve in 1856 was a watershed. We think of mauve and other aniline dyes for their impact on manufacturing, but they also remade microscopy. By 1862 histologists were using mauve to stain specimens, and the next year they expanded to aniline red, blue, and violet. The new dyes not only differentially stained anatomical structures but were also more standardized (making experiments easier to replicate) and easier to acquire. (For more on Perkin, see pages 8–9, 35 in this issue.)

Henry Clifton Sorby

The microscope began its diffusion from biology into other fields in Victorian Britain. In the early Victorian era, under the sway of Wordsworth and the Romantics, field scientists were thought to have an “authentic,” trustworthy relationship with nature through outdoor pursuits. Natural historians like Charles Lyell and Richard Owen controlled the institutions of British science until the 1850s. The mid-century unrest of Britain’s increasingly urbanized masses, though, led the country’s most influential naturalists to extol taming nature indoors. With proper instruments (the microscope and the aquarium) Britain’s urban masses could be occupied observing nature in their parlors—hence the late 1850s saw a glut of popular microscopy books, such as Edwin Lankester’s Half-Hours with the Microscope.

The Sheffield amateur Henry Clifton Sorby (1826–1908) beautifully exemplified this transition from natural history to microscopy. Sorby was born into Sheffield’s prosperous community of cutlers and toolmakers and was groomed for the family business. His mother (from a Sheffield family but London raised) had a larger vision for his future, however, and fostered Sorby’s scientific aptitude by hiring a tutor in mathematics, anatomy, and chemistry. When his father died, Sorby (aged 21) fashioned himself as an amateur “gentleman of science” by building his own laboratory, where his first experiments measured such trace elements as sulfur and phosphorus in plants—work inspired by the first translations of von Liebig’s works into English in the 1840s.

But Sorby was also an outdoorsman and natural historian. Late in life he even sailed a specially equipped yacht up and down East Anglia doing pioneering work in marine biology. Throughout his life he was an inveterate hiker, and his scientific pursuits naturally turned to geology. What made Sorby remarkable, though, was how he domesticated geology by combining it with microscopy and chemistry. When Sorby heard how lapidaries made thin slices of rock, he instantly realized this would allow light transmission through rock samples, making them amenable to microscopical investigation. By 1855 Sorby was studying microscopic fluid cavities in rock to gain a better understanding of the chemical and physical processes of rock formation.

From terrestrial rocks it was a small step to examining iron meteorites, and from meteorites a smaller step to looking at steel. In some ways, it is surprising Sorby did not study steel sooner. He was dedicated to local scientific organizations, was an officer of Sheffield’s Literary and Philosophical Society from age 22, and eventually became president of the town’s Firth College. It was perhaps inevitable that Sorby should take an interest in the material that made his town famous. Sheffield’s steel firms dominated the international market for cutlery and edge tools—even the coulters of John Deere’s plows—throughout the 19th century. Sheffield’s steelmakers long knew from ocular inspection that the quality of their product depended on its microstructure, the size and texture of its crystalline grains. But Sorby was perhaps the first to systematically prepare steel specimens by etching with acids for examination with a microscope and to relate microscopic observations to steel’s composition, treatment, and quality.

Émile Monnin Chamot

A consummate amateur, Sorby continually opened new fields and then moved on. He left his intellectual heirs working in universities and corporations in newly professionalized disciplines such as geology, metallurgy, and chemistry. His first generation of successors was in Europe—for instance, Ferdinand Zirkel for geology and Heinrich Behrens for metallurgy. Behrens provided the link to chemical microscopy’s most vociferous American proponent, Émile Monnin Chamot. Born in 1868 in Buffalo, New York, Chamot spent almost his entire adulthood at Cornell University. An undergraduate from 1888 to 1891, he wrote a senior thesis on “Some Curious Basic Salts of Lead” under George Caldwell (a student of Wöhler’s); after graduation he stayed to finish a Ph.D. on didymium. In 1897 Chamot finally took a brief sojourn from Cornell when, like many young American scientists of the day, he toured Europe to see cutting-edge scientific techniques firsthand.