Working in Glass

This essay will appear in our forthcoming book, “Making the Modern Laboratory,” to be published this summer.By Spencer WrightIt was a revolutionary idea in the 1830s, and it remains one today — virtually anyone can learn to make their own scientific equipment. With a few dollars’ worth of glass tubing, a flame, and a little practice, you can create all kinds of chemical analysis kits. Because the glass itself is airtight, you can control which chemicals go in, and because it’s clear, you can observe what happens to those chemicals as you manipulate them. If they don’t do what you intend, you can reignite the flame, modify your glass apparatus, and try again.This insight helped build the modern laboratory: Work wherever you want to, but work in glass, and you’ll reveal life’s most intricate mysteries.The person who catalyzed this idea, Justus Liebig, had the superlative career title of “Extraordinary Professor of Chemistry” (although his job’s “extraordinary” nature may have had more to do with its nominal compensation than anything else). In fact, Liebig wasn’t excited about the position he held, writing to his parents that he had “no great desire” for it. He would have preferred to stay in Paris — the center of the chemistry universe at the time, and a city where, even at twenty-one years old, Liebig had already begun to make a name for himself. But the University of Giessen had offered him a modest stipend to establish a lab, so, in 1821, Liebig accepted the constraints of small-town life and packed himself off there.Justus LiebigThe move (and modest budget) forced Liebig to perform chemical analysis in new ways. While in Paris, studying under the esteemed French chemist Joseph-Louis Gay-Lussac, Liebig had analyzed silver fulminate, letting it combust and then collecting the carbon dioxide that resulted. Because carbon dioxide is hard to weigh,1 Liebig had been taught to measure its volume using an eudiometer, a type of inverted, graduated cylinder where gases could be trapped and their volume read from markings on the glass. This device was costly to make and finicky to use, and Gay-Lussac relied on specialized glassblowers to help design, produce, and maintain it. With such infrastructure missing in Giessen, Liebig’s research stalled.

If necessity is the mother of all invention, then ambition is its accelerant. Dissatisfied with teaching pure theory at the University, Liebig founded an independent institute to impart the tactile skills of applied chemistry. And dissatisfied with the equipment available in Giessen, Liebig traveled back to Paris to learn glassblowing — a skill he then passed on to his students. A kaliapparat, with its characteristic five spheres, was used for elementary chemical analysis. Credit: Liebig Museum in Giessen, Germany.Even as he gained these practical skills, he picked intellectual fights with prominent chemists in Paris and Berlin, insisting that their methods of analyzing organic molecules (which measured carbon and nitrogen together from a single volume of mixed combustion gases) were flawed. By 1830, Liebig knew how to make his own glassware and was now prepared to back up his published claims of superior analytical excellence.The result was the Kaliapparat, a twisted glass triangle that Liebig used to analyze the composition of morphine.2 The principle behind it was simple: Fill the bottom of the Kaliapparat with potassium hydroxide, then force morphine’s combustion gases through it. As the gases bubbled through the Kaliapparat’s bulbs, any CO₂ present would react with the potassium hydroxide, trapping the carbon but allowing the rest (hydrogen, nitrogen, and oxygen) to pass through. Then, by weighing the Kaliapparat and subtracting its pre-reaction mass, Liebig could determine exactly how much carbon, by mass, had been in the original morphine sample.As an analytical tool, the Kaliapparat was middling. Liebig’s original goal had been to determine morphine’s nitrogen content, which proved challenging given that the nitrogen passing through the apparatus commingled and reacted with other gases. In fact, historian Catherine Jackson states in her book Molecular World that it was even self-admittedly a failure. “In private, Liebig was even more scathing. As he admitted to Berzelius [a dominant figure in European chemistry and a correspondent], his method of nitrogen determination was ‘tiresome, time-consuming and, in a word, quite unbearable,’ while nitrogen’s side reactions had driven him to ‘despair,’” she writes. However, the Kaliapparat was indeed reliable for measuring carbon — and at a much lower cost than the volumetric-based Parisian equipment of the day.

So when he published his results in 1831, Liebig simply de-emphasized the nitrogen analysis performed with it and focused on the glassware itself, christening it “A New Apparatus.”It would take a few more years, however, for the vessel to gain widespread adoption. In 1833, Liebig slipped instructions on how to make a Kaliapparat into an article he had translated from French to German. In 1834, one of his assistants also demonstrated how to make a Kaliapparat at a chemistry meeting. And, in 1839, Liebig published a textbook on organic analysis that included instructions on the making and use of such glass vessels. According to Jackson, Liebig’s effort to publicize the device — and encourage other chemists to make their own — was “explicitly pedagogical.” Liebig sought “to overturn Parisian chemical orthodoxy … [wanting] chemists everywhere to see and understand, to make and use the Kaliapparat and to prove its worth by widespread replication.”Finally, Liebig’s efforts paid off, and the 1840s became a golden era of amateur glassblowing. Chemists everywhere took up the torch, replicating Liebig’s Kaliapparat (a stylized version of which would be used in the American Chemical Society logo in the 20th century) and producing designs of their own. Glass vessels evolved, and organic analysis flourished as scientists could finally determine repeatable values for a sample’s carbon content. But most importantly, glassblowing established itself as a need-to-know process for anyone doing serious chemistry.Page from a glassware catalog, ca. 1860.While Liebig’s proselytizing encouraged chemists to learn glassmaking, it also helped that glass itself was so cheap and easy to make. Glassmaking materials (silica sand, soda ash, and limestone) were readily available. As a result, glassblowing became professionalized. Entire lab glassware catalogs sprang up, many of which contained both prices and instructions on how to make one’s own instruments.One prominent glass dealer was English chemist and publisher John Joseph Griffin, who in his 1832 book Chemical Reactions promoted the use of tumblers (later known as “Griffin beakers”).

As the need for professional lab glassware suppliers emerged, Griffin established a shop in Covent Garden in 1852. By the time he published his 1866 lab equipment catalog, it included an adaptation of the Kaliapparat. For one shilling and sixpence, a chemist could purchase “Liebig’s Potash Apparatus,” complete with furnace, combustion tube, desiccant chamber, Kaliapparat, and vulcanized caoutchouc (rubber) connectors. For two shillings and sixpence, a specially modified Kaliapparat, made by professional glassblower Heinrich Geissler, was also available.This modified device, just one of many similar tools that Geissler invented in the latter half of the 19th century, was designed such that it could be set upright on a tabletop. (Liebig’s triangular design, intended to be suspended from a scale, would simply fall over if set on a surface.) Beyond its basic geometry, Geissler made refinements to increase the Kaliapparat’s accuracy, adding integrated desiccant tubes as well as embedding little glass discs within its three glass bulbs, which forced the combustion fumes to bubble more vigorously (and therefore react more fully) as they passed through the potassium hydroxide.Geissler’s Kaliapparat is especially striking considering how difficult it would have been to fashion in 1866. At the time, a glassblower’s flame was not made by compressed propane and oxygen, as they are today, but by simply blowing air over an alcohol or oil lamp — or, in some cases, over a charcoal fire. “You were either using your breath or a foot bellows,” choreographing hands, mouth, and feet to generate temperatures in excess of 700°C, says Tracy Drier, a master glassblower at the University of Wisconsin. Today’s glassblowers work with oxy-propane torches that render such contortions obsolete, a convenience Liebig and Geissler could not have imagined.Liebig and Geissler would have also been struck by the material properties of Tracy’s glass, as the glass formulations of their day left much to be desired. Both soda-lime formulations and leaded glass were vulnerable to attack by water and acids, and would become pitted and cloudy after repeated use.

They also needed to be carefully handled and were sensitive to sharp changes in temperature. Even Bohemian potash glass, known for being colorless and fairly workable, contained impurities (iron contamination could introduce a faint greenish tinge) as well as bubbles, seeds, and striations (thin waviness from incomplete melting and mixing).Perhaps unsurprisingly, the features of glass that late-19th-century scientists desperately wanted to improve upon were its optical qualities. This was especially true for those working in the burgeoning laboratory sciences that relied heavily on microscopes. And the key to better microscopes was better lenses — a technology which was being developed primarily in Jena, a town just 250 kilometers west of Giessen.Blowing pipettes for laboratory use in a glass factory (ca. 1890s).One of the major challenges lenses contend with is light dispersion. When light passes through glass, different frequencies bend by different amounts (the same phenomenon that creates rainbows in prisms). Dispersion is not an issue for lab glassware. A chemist wouldn’t care much if their Kaliapparat were to create little rainbows on their workbench. But in the nineteenth century, developments in the glass industry tended to come from optics (a big market) rather than beakers (a relatively small one). In a microscope or telescope, dispersion results in blurry, unfocused images as the light’s constituent parts fail to converge at a single focal point.It was the chemist Otto Schott who took up the creation of low-dispersion glass. Schott grew up in the glass factory his father managed and later studied the chemistry of glass at the University of Jena. When he completed his degree in 1875, he returned home to Witten, where he kept working on glass formulations, and in 1879, managed to melt a batch with especially high lithium content. Confident that he had found a low-dispersion formulation, he sent a sample to Ernst Abbe, a professor at Jena who had been advocating for a systematic study of glass’s optical qualities.Taken by the young Schott’s enthusiasm, Abbe invited Schott back to Jena to join him and microscope-maker Carl Zeiss in forming the Glass Technology Research Station. The collaboration, credited as “one of the greatest and most productive associations in the history of glass composition,” proved immensely fruitful.