Rouelle, Guillaume-François

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(b. Mathieu, Calvados, France, 15 September 1703; d. Passy, Seine, France, 3 August 1770)

chemistry, geology.

Born in a village now on the outskirts of Caen, Rouelle attended the University of Caen, where he reportedly earned a maitre-ès-arts. About 1730 he went to Paris and became apprenticed to an obscure German pharmacist named J. G. Spitzley. By 1740 he was giving lectures on chemistry and pharmacy in the Place Maubert, not far from the Jardin du Roi; and he soon attracted the attention of Buffon, who, in 1742, appointed him to the post of demonstrator in chemistry at the Jardin. In 1746 Rouelle moved his laboratory to the rue Jacob (faubourg St.-Germain), where he taught private courses for the rest of his active career. Once admitted to the Company of Apothecaries of Paris in 1750—even though he had not completed the ten years of training required of licensed pharmacists—he added a pharmacy shop to his laboratory. This shop, still in existence, was later operated by Hilaire-Marin Rouelle and eventually passed into the hands of chemist and pharmacist Bertrand Pelletier.

Rouelle’s duties at the Jardin required him to perform experiments to illustrate the theories propounded by the professor of chemistry, at that time Louis-Claude Bourdelin, a chemist of no particular distinction. Since, in an arrangement without parallel, Rouelle’s title was actually demonstrator “sous le titre de Professeur,” he also delivered lectures on theory; and his courses were thus complete and independent of Bourdelin’s. Like all courses at the Jardin, Rouelle’s were open to the public; those he taught in the rue Jacob were more detailed and were attended by a fee-paying clientele.

The content of Rouelle’s lectures was not wholly original; many of his experiments resembled those in Lemery’s popular Cours de chymie (1675 and subsequent editions). But he did improve upon traditional techniques in organic analysis by moderating the temperatures employed so that reagents and distillates were not destroyed. He also lectured on the classification of salts, the subject of his most important publications. Examining both crystal form and chemical composition, he distinguished neutral salts from those with “an excess of acid” and those with “very little acid.” Not only did his definitions of acid, alkali, and salt bring precision to an area then in a state of confusion, but his published memoirs also revealed an experimental skill and clarity of thought that were generally not the qualities remarked upon by contemporaries who attended his lectures.

Among Rouelle’s innovations was his adoption, with modifications, of the phlogiston theory of Stahl and the conclusion put forth by the English physiologist Hales (denied by Stahl) that air can be a chemical constituent of matter. These two ideas became part of Rouelle’s own synthesis, the fundamental tenet of which was that earth, air, fire (phlogiston), and water all serve as both chemical elements and physical “instruments” that assist in the process of chemical change. Most contemporaries did not fully recognize the originality of this theory, assuming instead that Rouelle was transmitting the ideas of his predecessors or that he was simply reviving the four elements of Aristotle. It was often assumed, too, that phlogiston in particular had entered into French chemistry early in the century. The evidence, however, suggests that the phlogiston theory was accepted in France only in mid-century and then only as part of a broader chemical theory; the isolation of phlogiston from this context seems to date from the 1770’s.

How Rouelle became familiar with the work of Stahl and other German chemists remains mysterious. Contemporaries sometimes described him as untutored and even semiliterate, but such reports are undoubtedly exaggerated and may mean only that his manners were boorish and provincial. One pupil, Antoine Monnet, believed that Rouelle gleaned much information from his many foreign students. Certainly Rouelle was sufficiently aware of the value of German (and Latin) works to advocate their translation into French, and one student attributed to his influence the translation by d’Holbach of several treatises by Stahl.1 Other pupils, including P.-F. Dreux, J.-F. DeMachy, and A.-A. Cadet de Vaux, reveal that Rouelle inspired or even specifically requested the translations that they themselves produced.

Early in his career, Rouelle introduced into his lectures some discussion of the structure of the crust of the earth. He classified all geological formations into two groups: the unfossiliferous, largely granitic masses forming a primitive core; and the more recent, fossiliferous, sedimentary strata superimposed upon the primitive. During the 1760’s, he modified this scheme to include an intermediate series of strata corresponding to the Coal Measures. Like other aspects of his teaching, this classification was uncommon when he first taught it—reputedly in about 1740—and almost a cliché when he retired, since it was to be suggested, independently, by many of his French and foreign contemporaries. Rouelle’s importance as a geologist lies in the fact that he offered elementary instruction, inspiration, and some fruitful ideas to two talented pupils, Lavoisier and Desmarest.

No reading or summary of the content of Rouelle’s lectures can quite account for the impact he had upon his contemporaries. He was universally considered to be an extraordinary teacher, even in an era of such teachers as Joseph Black, Boerhaave, and Bernard de Jussieu. But he differed from these men in that his style was unusually stirring and flamboyant. The following description by Vicq d’Azyr is not atypical:

His eloquence was not a matter of words; he presented his ideas the way nature does her productions, in a disorder which was always pleasing and with an abundance which was never wearisome.… When he exclaimed: Listen to me, for I am the only one who can prove these truths for you, one knew that this was not evidence of vanity, but rather the transport of a soul fired by boundless zeal.2

Less typical in its emphasis upon Rouelle’s competence as a chemist is a passage by Cadet de Vaux: “I am proud of having learned from him the principles of my profession, [which I did] on the advice of my brother [L.-C. Cadet] who, although he could have taught me very well indeed, thought he could do no better than to turn me over to Rouelle.”3

Rouelle’s more distinguished pupils included Lavoisier, Desmarest, Macquer, Venel, D’Arcet, and Bayen. As impressive is the list of nonscientists known to have attended his lectures: Diderot, d’Holbach, Jean-Jacques Rousseau, Malesherbes, and Turgot.

Among the distinctions awarded Rouelle were memberships in the Académie Royale des Sciences (1744) and in the academies of Stockholm and Erfurt. He also served on royal commissions charged with the investigation of such subjects as a cure for distemper in cattle, improvement of the refining of saltpeter, and the examination of alloys used in coinage. In 1753 he succeeded C. F. Geoffroy as inspector general of pharmacy at the Hötel-Dieu. As Rouelle’s health deteriorated, his lectures at the Jardin du Roi were sometimes delivered by his younger brother, who was appointed demonstrator in chemistry in 1768.

Rouelle’s personal life and professional career in many ways remain obscure because of the limited nature of the available sources; this problem is so pervasive and so crucial that it deserves some analysis. Rouelle himself published little and seems to have left no manuscripts; and the information about him that is recorded by his contemporaries is of varying reliability, largely anecdotal, and far from complete. The content of his chemistry lectures is known solely in the manuscript versions left by his students. Many manuscripts are, in fact, traceable to the notes of a single pupil, Diderot; and they therefore record Rouelle’s teachings only for the period 1754–1758. While texts of other dates exist, they are not numerous (and those later than 1758 are often derivatives of the Diderot tradition) and do little to reveal any development in Rouelle’s ideas during his long career. Furthermore, contemporaries sometimes attributed to Rouelle ideas not to be found in the manuscripts, and the accuracy of such reports cannot always be tested. Rouelle intended to publish a textbook based on his lectures—and a group of disciples, including his younger brother, had similar plans—but no such work ever appeared.

The sources for his activities in areas other than chemistry are even more slender and indirect. He is said to have frequented the Café Procope and Holbach’s salon, but little is known about his relations with the philosophes he met there. A few extant manuscripts supply virtually all that is known about the courses in pharmacy that he taught for about thirty years. Weekly gatherings of colleagues and selected students are said to have taken place at his laboratory, but there is no record of conversations and almost none of participants.


1. Bibliothèque de l’Institut de France, Paris, MS 6036, fol. 4r.

2. Félix Vicq d’Azyr, Oeuvres, J.-L. Moreau de la Sarthe, ed., I (Paris, 1805), 280.

3. J. R. Spielmann, Instituts de chymie, trans. by A.-A. Cadet de Vaux, I (Paris, 1770), xx–xxi.


Standard bibliographies, including the published catalogues of the Bibliothèque Nationale and the British Museum, normally confuse Rouelle and his brother; a good working rule in these cases is to assume that items published after 1770 are by Hilaire-Marin rather than Guillaume-François. A bibliography of original and secondary works and some discussion of MSS are in R. Rappaport, “G.-F. Rouelle: An Eighteenth-Century Chemist and Teacher,” in Chrmia, 6 (1960), 68–101, and the sequel, “Rouelle and Stahl—The Phlogistic Revolution in France,” ibid., 7 (1961), 73–102; and Jean Mayer, “Portrait d’un chimiste: Guillaume-François Rouelle (1703–1770),” in Revue d’histoire des sciences et de leurs applications, 23 (1970), 305–332. The following are addenda to these articles.

There is no published checklist of MSS, but most are in France and are readily found listed in the series Catalogue général des manuscrits des bibliothéqucs publiques de France. Excellent copies in England are at the Wellcome Historical Medical Library, London, and the Science Library, Clifton College, Bristol. The MS once owned by Denis I. Duveen is now at Cornell University, Ithaca, New York. Many MSS do not contain the lectures on geology. MSS in the Diderot tradition stem from Rouelle’s private courses, as is shown by the copy at the Bibliothèque Municipale of Aire-sur-la-Lys (Pas-de-Calais). An unusually complete version of the public lectures is at the Bibliothèque Centrale, Muséum National d’Histoire Naturelle, Paris, MS 2542. There are few MSS of the pharmacy lectures; these include copies at the Bibliothèques Municipales of Lille and Arras, the Wellcome Historical Medical Library, and the Faculté de Pharmacie, Paris.

Two periodicals, the Avantcoureur and the Journal de médecine, chirurgie, pharmacie, &c., are valuable for notices and sometimes descriptions of the content of courses offered by Rouelle, his brother, and their rivals. The papers of Antoine Monnet (école des Mines, Paris, MSS 4678, 4685) supply impressions and details by a disciple of questionable reliability. Anonymous notes for a eulogy of Rouelle are in the Bibliothèque de l’Institut de France, Paris, Fonds Cuvier, tone 182, pièce 9.

Rhoda Rappaport