Recherches Chimiques

Detail of a foldout engraving from Recherches chimiques sur la végétation by Théodore de Saussure, 1804.

Science History Institute/Douglas A. Lockard

Materials Matter

Emily Pawley reviews Ursula Klein and Wolfgang Lefèvre’s Materials in Eighteenth-Century Science: A Historical Ontology.

Ursula Klein; Wolfgang Lefèvre. Materials in Eighteenth-Century Science: A Historical Ontology. Cambridge, MA: MIT Press, 2007. 355 pp. $40.00.

In their new book Materials in Eighteenth-Century Science: A Historical Ontology, Ursula Klein and Wolfgang Lefèvre draw the study of 18th-century chemistry away from abstract models—“atoms, corpuscles, and Newtonian Forces”—and root it instead in a complex world of materials: balsams, resins, fats, salts, alloys, mineral acids, roots, leaves, bones, hair, and blood. Throughout the 18th century, they argue, chemists were experts on the materials of everyday life; to understand their practices, then, historians should examine their ways of classifying and defining these materials. Klein and Lefèvre clearly describe the scope and purpose of chemists’ work, break down anachronistic boundaries between pure and applied science, and map the movement of knowledge between chemists and artisans in “apothecary’s shops, foundries, assaying laboratories, arsenals, dye manufactories, distilleries, coffee shops, and so on.”

The authors begin by tracing a crucial development in the history of chemical classification: the growth and increasing centrality of the 18th-century concept of the compound. In making compounds, or “mixts,” chemists and alchemists of the 16th and 17th centuries felt that they were part of an act not of addition but of generation. Mixts did not contain the ingredients that were used to make them; instead, they were the “descendants” of their “parent” substances (often identified as male and female) and so were imbued with their parents’ qualities. Klein and Lefèvre argue that through the increasing use of reversible reactions, in which compounds were made and their parent components recovered, 18th-century chemists came to understand compounds as assemblages of traceable component substances, held together by chemical “affinities,” whose proportions determined the compound’s properties. This way of understanding materials slowly became central to the act of classifying them.

Klein and Lefèvre then examine the Tableau de nomenclature chimique, a table that appeared in the Méthode de nomenclature chimique, published by Guyton de Morveau, Lavoisier, Berthollet, and Fourcroy in 1787. Historians have understood this table as a major development in Lavoisier’s chemical revolution and an attack on the theory of phlogiston. For Klein and Lefèvre the Tableau serves another purpose: it describes only a limited number of possible materials: one class of "simple substances,” which could not be further reduced, such as light or oxygen; six classes of “pure substances” which could be put into, retrieved from, and traced through reversible reactions; and five classes of compounds, made of substances from the other classes. The Tableau is thus an embodiment of composition-based classification, and it allows Klein and Lefèvre to study the roots of the modern concept of compounds.

In this discussion, Klein and Lefèvre expand their argument for the significance of artisanal knowledge. In describing compounds, the table concentrates on specific reversible reactions, particularly those that create neutral salts, acids, gases, and metal oxides and alloys. Klein and Lefèvre show that knowledge of metals and salts was derived from the work of metallurgists and apothecaries, who developed reversible reactions in the course of their labor. Further, the authors show that much of the Tableau drew not only on a previous affinity table, but even on phlogiston theory—the very theory its authors purported to attack. By examining this icon of the chemical revolution, Klein and Lefèvre show the deep roots of a work that eminent scholars have often described as a revolutionary break with the past.

While the Tableau might have encompassed salts, gases, and metals, it could not be used to classify the majority of materials that chemists studied, particularly animal and plant extracts and raw minerals. While these substances could be broken down, they could not be synthesized, and so the reversible reaction-based concept of composition did not apply. In the rest of their book Klein and Lefèvre examine less familiar forms of classification applied to plant substances.

The classification of 18th-century plant material had its own terms and timeline. Until well into the 19th century, chemists categorized plant materials according to their origins, practical uses, and perceptible properties while they simultaneously struggled to identify the qualities that differentiated them from minerals or pure substances. These struggles led to a different series of turning points from those described in the classic stories of chemistry: the study of “organized matter” that began in the 1750s, the creation of the category “organic substances” in the 1790s, and finally, in the 1820s and 1830s the growth of carbon chemistry, which used the array of new substances drawn from coal tar and the development of organic syntheses to connect the organic to the compound.

A warning to readers: this work is dense and elaborately structured, written neither for the novice nor for the faint-hearted. Its authors presuppose a considerable knowledge of 17th- and 18th- century chemistry and, in emphasizing theoretical points over a narrative, they obscure the chronological sequence that underpins the work, leading in places to a series of awkward repetitions and retreats. However, in refocusing our attention on the world of substance the book not only offers a new perspective on 18th-century chemistry, but also promises rich stores of material to be mined by future historians.