Essays on Science and SocietyBEYOND THE IVORY TOWER

Not a Pure Science: Chemistry in the 18th and 19th Centuries

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Science  05 Nov 2004:
Vol. 306, Issue 5698, pp. 981-982
DOI: 10.1126/science.1089888

Chemistry was first introduced as an academic discipline in medical faculties, academies, botanical gardens, and museums in the late 17th century. Over the next 100 years, it became an established part of the European intellectual world. Eighteenth-century chemists were teachers and professors, authors of learned books and experimental essays, members of academies and scholarly societies, and frequent visitors to coffee shops and salons. Yet, they differed markedly from other savants of the time. They were passionate experimenters who spent many hours in their laboratories. Furthermore, they were learned practitioners: apothecaries, metallurgical officials, consultants, inspectors of manufactures, entrepreneurs, and members of state committees and technological boards (1, 2).

The connection between chemistry and pharmacy went back to medieval times. The distillation vessels used in 18th-century apothecaries' laboratories originated in the late medieval alchemical tradition. Chemical operations such as distillations and extractions with solvents were also not invented in apothecary guilds but learned from 15th-century alchemists. Pharmacopoeias and other apothecary books of the 18th century included recipes for hundreds of chemical medicines originally introduced by the Paracelsian medical-chemical movement. Inversely, almost all 18th-century chemical textbooks presented numerous recipes for the fabrication of medicines and described their properties and medical virtues.

The chemist-apothecary was a widely respected persona throughout 18th-century Europe. Andreas Sigismund Marggraf (1709–1782), for example, had completed an apothecary apprenticeship and, between 1735 and 1753, administered his father's apothecary shop in Berlin. He later became famous for his chemical experiments and publications, as well as for his directorship of the Berlin Academy's physics class. Marggraf had also learned assaying with Johann Friedrich Henckel (1678–1744) in Freiberg, done the first experiments for the extraction of sugar from beets, and was an ambitious naturalist who owned a large mineral collection. Many 18th-century chemist-physicians also produced and sold their own chemical remedies (3).

Inventory of a 17th- to 19th-century apothecary's laboratory. CREDIT: FROM (7).

A number of 18th-century chemists also were involved in mining and metallurgy, particularly in Germany and Sweden. Travels to mining districts and visits to mines, salt-works, and metallurgical factories were an important part of the technical education of 18th-century chemists. In this way, they gathered information about the processes of mining, smelting, and assaying; the extraction of salts; and the properties and uses of machines and materials. They brought back from their travels samples of minerals, as well as improved natural historical knowledge about minerals, mountains, and strata of rocks.

But not only occasional travel created bonds between academic chemistry and the world of mines and smelting factories. From 1683, the Swedish Board of Mines maintained a chemical laboratory where chemist-mining officials analyzed minerals and mapped the Swedish mineral resources (4). In the mid-18th century, this laboratory became a pioneering place for the use of the blowpipe in mineral analysis. Many German chemists also held positions as mining and metallurgical councilors in mining towns such as Freiberg, Brunswick, and Schemnitz, where they were charged with the control and improvement of the technology, economy, and organization of labor in mines and smelting works and with the analysis of minerals. Most of them were also teachers, authors of chemical and metallurgical treatises, and members of academies and scientific societies. This dual carrier as chemist and salaried mining and metallurgical councilor continued throughout the 18th century.

Eighteenth-century chemists were also actively involved in other arts and crafts. For example, in the 1740s, the Prussian king Frederick II commissioned three chemists to study the manufacture of porcelain. One of them, Johann Heinrich Pott (1692–1777), established a porcelain works in Freienwalde, funded by the Prussian king. In France, Joseph Pierre Macquer (1718–1784) made similar investigations, which culminated in the production of the first French porcelain at Sèvres.

Chemists were also involved in the search for surrogates for precious imported commodities such as sugar, tobacco, coffee, brandy, and liqueurs. The extraction of sugar from beets, for example, which had been initiated by Marggraf in the 1840s, was pursued by German chemists. Most successful was Franz Carl Achard (1753–1821), who in the 1790s received a salary and an estate from the Prussian king Friedrich Wilhelm II to establish a sugar manufacture. In the royal manufactures of France, many chemists held leading positions as inspectors (5).

It was less their theoretical knowledge than their experimental and natural historical knowledge about a broad range of materials, their ability to identify materials, experimental skills, and their familiarity with chemical analysis that equipped chemists for their various technological occupations as hybrid technologist-savants. Until the mid-18th century, the equipment in academic chemical laboratories did not differ substantially from that of apothecaries' shops, assaying and smelting workshops, and distilleries. We know from drawings of chemical laboratories and instruments, and from their verbal descriptions, that 18th-century chemists relied heavily on the instruments and materials provided by ordinary craftsmen and merchants. Their smelting and testing furnaces, bellows, crucibles, calcination dishes, and balances were largely the same as those used in the workshops of assayers and smelters. Evaporation vessels, crystallizing dishes, phials, retorts, alembics, pelicans, receivers, and transmission vessels were common instruments both in the chemical and pharmaceutical laboratory (see the figures), while simple retorts and receivers were shared with distillers for fabricating mineral acids, alcoholic spirits, and fragrant oils.

As these technological occupations illustrate, chemistry never was a pure science. But in the early 18th century, chemists began to develop areas of inquiry that were largely unfamiliar outside of academia. They refined techniques of chemical analysis, restructured the relations between chemical analysis and theories of chemical composition, explored cycles of analysis and resynthesis of substances in the laboratory, and analyzed experimental results to establish laws of chemical affinity between substances.

An 18th-century chemical laboratory. CREDIT: DEUTSCHES APOTHEKEN-MUSEUM, HEIDELBERG

These scientific activities culminated in the so-called chemical revolution in the last third of the 18th century, but they were largely confined to explorations of inorganic substances (mineral acids, alkalis, metals, and salts) that could be purified to a comparatively high degree with the available laboratory techniques. By contrast, substances extracted from plants and animals were largely excluded from these developments. Until the early 19th century, plant and animal chemistry—or “organic chemistry” as it was then often called—included inquiries into the natural history and physiology of plants and animals and maintained most of its traditional bonds with pharmacy and other arts. Between the late 1820s and the 1840s, this changed fundamentally when, spurred in particular by the work of French and German chemists, a new form of organic or “carbon chemistry” emerged.

In the new carbon chemistry, the investigation of the constitution (later “structure”) of organic compounds and their substitution reactions became a prominent objective. This objective was largely disconnected from pharmacy and other commercial applications. Substitution reactions procured chlorinated hydrocarbons and other organic molecules that were unknown both in nature and the extant commercial world. Most chemists involved in the emerging subdiscipline of carbon chemistry—such as Justus Liebig (1803–1873) and Friedrich Wöhler (1800–1882) in Germany and Jean Dumas (1800–1884) and Auguste Laurent (1808–1853) in France—maintained their connections with pharmacy and industry in areas other than carbon chemistry. However, the applicability of substitution products and the usefulness of investigations into the structure of organic compounds were not on their agenda.

Yet, from the mid-1850s, it was exactly this new type of chemical expertise that became most useful in the emerging synthetic-dye industry. Why was this the case? The connections between chemical science and technology in the new synthetic-dye industry that began to develop after William Henry Perkin's synthesis of mauve in 1856 are complex. But one contribution of the science of carbon chemistry to the synthetic-dye industry was clearly crucial: chemical theory embodied in chemical formulae. Linear chemical formulae, like H2O for water, had been introduced by the Swedish chemist Jacob Berzelius (1779–1848) in 1813. They presented the composition of chemical compounds according to a theory of definite quantitative units or portions of substances. With atomism, this new quantitative theory shared the assumption of discontinuous composition of substances. But the algebraic form of Berzelian formulae avoided narrow definitions in terms of “atoms,” which many chemists rejected as metaphysical entities. Letters, numbers, and additivity were sufficient to represent quantitative units of elements and discontinuous composition of compounds. Different arrangements of letters visually showed how units of elements were combined with each other. The structural formulae of the 1860s displayed chemical and spatial arrangements in an even more pictorial form.

Beginning in the late 1820s, chemists used chemical formulae as tools on paper to model the constitution of organic compounds. Using chemical formulae as paper tools, chemists reduced the complexity in the “jungle of organic chemistry” (F. Wöhler). Chemical formulae enabled them, for example, to order organic chemical reactions by formula equations that distinguished between a main reaction, side reactions, and successive reactions.

In the 1860s, chemical formulae had become an emblem not only of academic chemistry but also of the synthetic-dye industry. Quantitative chemical theory was implemented in the new alliance between carbon chemistry and the synthetic-dye industry in the form of paper tools that were subordinated to chemists' experimental and technological goals (6). Compared with the connections between academic chemistry and the arts and crafts in the 18th century, this role played by chemical theory and formulae was a novelty.

References and Notes

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