HOMBERG, WILHELM

(b. Batavia, Java [later Jakarta, Indonesia], 8 January 1653; d. Paris, France, 24 September 1715),

chemistry. For the original article on Homberg see DSB, vol. 6.

Homberg has emerged as a key figure in the history of chemistry. New studies indicate his important innovations in chemical theory and techniques and more accurately situate him in his due context as a major figure of the early eighteenth century.

Essentially all biographical sketches of Homberg, including that of the original DSB article, drew uncritically from Bernard de Fontenelle’s 1715 Éloge de Homberg. But since the publication of the earlier DSB, new studies have revealed errors of fact and chronology in that account, and thus it is worth recapitulating his biography in the light of more recent findings.

Life and Travels . Homberg was born in 1653 (not 1652) at the Dutch East Company’s settlement at Batavia on the isle of Java. His father, Johann, a native of Quedlinburg in Sachsen-Anhalt, was an officer for the company, and Homberg’s mother, Barbara, of Dutch origin, was the widow of Antoni Beer, another company officer. Wilhelm was the fourth of six children and the younger of two sons. The family left Java for Europe in the mid-1660s, settling first in Amsterdam. Wilhelm was sent for a career in law, matriculating at Jena in 1672 and then Leipzig in 1675, where he defended his thesis in March 1676. He then began to practice law at Magdeburg, where he started to develop an interest in natural philosophy and mechanics. These interests were fostered by Otto von Guericke, who apparently shared some of his secrets with the young Homberg.

Homberg then embarked on almost fifteen years of travel, meeting, and trading secrets with notable natural philosophers and visiting natural and industrial sites across Europe. Homberg journeyed first to Italy, studying (without matriculating) at Padua in 1677 and then traveling to Bologna, where he acquired or rediscovered the secret of how to render the celebrated “Bolognian stone” (a native barium sulfate) phosphorescent by means of a careful calcination. Thereafter he worked with the instrument maker Marco Antonio Cellio in Rome, possibly imparting to him the secret of the Bolognian stone in exchange for training. After a possible trip through France, Homberg went to Germany to learn about new phosphorescent materials: Baldwin’s “hermetic phosphorus” (phosphorescent calcium nitrate) and Johann Kunckel’s white phosphorus. Homberg traded von Guericke’s Wettermännchen, a kind of a barometer (not a hygrometer), for the recipe for the latter. Armed with a letter from Gottfried Wilhelm Leibniz, Homberg journeyed in 1679 to England, where he met Robert Boyle, possibly assisting him with his attempts at that time to prepare phosphorus and receiving alchemical secrets in return. There is no evidence for the claim that Homberg obtained an MD at Wittenberg around this time.

Homberg visited mining operations in eastern Europe (as far down the Danube as Belgrade), then in Sweden, where he may well have associated with Urban Hjärne in 1681. After touring France he settled in Paris in 1682. Here he came to the attention of Jean-Baptiste Colbert and began collaborating with members of the Académie Royale des Sciences, particularly Edme Mariotte, on studies of the air, phosphorus, and the freezing of liquids. In late 1682 Homberg converted to Catholicism (for which his father disowned him) and in January 1683 was naturalized in France. After Colbert’s death he was employed by Louis-Armand Bonnin, abbé de Chalucet, on transmutational endeavors. Although this project did not produce precious metal, it did yield a spontaneously inflammable powder (produced initially from roasted human feces) long known as “Homberg’s pyrophorus.” In 1685 Homberg, his French patronage at an end, went to Rome, where he associated with the Accademia Fisicomatematica Romana, worked on mechanics and microscopy, wrote a treatise on the generation of animals, and probably practiced medicine. He visited Paris in 1687 in order to demonstrate phosphorus, a new air pump, and the Bolognian stone to the academy, and he may have resettled in Paris shortly thereafter. In late 1691 he was admitted to the academy and spent the rest of his life in Paris as one of the most active academicians of the era.

In 1702 Philippe II, duc d’Orléans and later regent of France, chose Homberg as his tutor in chemistry and built a magnificent laboratory at the Palais Royale where they worked together. In 1704 Homberg became Philippe’s first physician. In 1708, at age fifty-five, Homberg married Marguerite-Angélique, the forty-year-old daughter of his recently deceased colleague Denis Dodart; the couple produced no children. In early 1712, following the sudden deaths of the dauphin and dauphine, Homberg was nearly taken to the Bastille for questioning (owing to rumors that they had been poisoned), but this action was forbidden by the king. After a lengthy intestinal malady, Homberg died in 1715 and was buried at Saint-Eustache; his funeral monument was destroyed in the Revolution.

Scientific Work . Homberg worked on many scientific issues during his lifetime. Much of his work before 1700 focused on pneumatics and the vacuum, using an improved air pump of his own design. He examined the sprouting of seeds, the exploding of Prince Rupert’s drops, the freezing and evaporation of liquids, and other phenomena in the vacuum. He was the first to propose distillation at reduced pressure to prevent thermal decomposition. He also designed instruments, made botanical, anatomical, and entomological observations, and was called upon by the academy regularly to examine or improve technological and commercial processes.

Homberg’s greatest contributions, however, were in chemistry. His work shows a keen interest in weight determinations and the need for pure and standardized reagents. He was the first to attempt to standardize solutions and to measure the various “strengths” of acids and alkalies based on their relative ability to neutralize each other. Throughout his career at the academy he worked to test earlier chemical theories and to determine the constituents of mixed bodies. To this end he examined the vast quantity of plant analyses carried out at the academy since the 1670s and conducted a series of carefully planned experiments that often extended over three or four years. In his own analyses he used a system of weight determinations that has been seen as the foundation for the more celebrated “balance-sheet” method of Antoine-Laurent Lavoisier, who knew and valued Homberg’s work.

For the last twenty years of his life he worked on the presentation and illustration of his chemical theory in a textbook. Parts were serially published in the academy’s Mémoires under the title Essais de chimie (1702–1710), and although the full manuscript was complete at the time of his death it remained unpublished. Homberg’s Essais mark a crucial break in the French didactic tradition; for the first time, pharmaceutical and commercial preparations are absent and the focus is clearly on the derivation of a comprehensive, coherent chemical theory from experimental results. Homberg embraced the five-principle theory of Étienne de Clave and others but also held that these five—mercury, sulfur, salt, water, and earth—were not the ultimate constituents of mixed substances but were instead useful and sensible categories of substances separated by chemical analysis. The centerpiece of Homberg’s system is his sulfur principle, the common substance contained in all sulfurous substances. In 1705, after lengthy experiments, he identified this sulfur principle with light. According to Homberg, light can incorporate with the other principles, change their figure and arrangement and add to their weight, and is the sole source of change and activity in matter. The exchange of sulfur/light in different forms explains most chemical reactions. Homberg’s theory reflects his lifelong fascination with the interaction of light with matter, exemplified by his work with phosphorescent materials, including his discovery of the piezoluminescence of fused calcium chloride (erroneously called an explosive chlorate in the original DSB article). But it was also certainly greatly promoted by the experiments he carried out with the enormous burning lens (not mirror) constructed by Ehrenfried Walther, Graf von Tschirnhaus, and purchased by the duc d’Orléans in early 1702.

Viewing the metals as compound bodies, Homberg also continued to believe in the possibility of metallic transmutation, even while the official stance of the academy increasingly frowned upon it. He knew the traditional chrysopoetic literature very well and was particularly influenced by the writings of Eirenaeus Philalethes (George Starkey). Many of his Essais are built around experiments with a specially prepared “philosophical” mercury, the key starting material for the philosopher’s stone, and Homberg claims to have had success in transmuting a portion of it into gold by long periods of heating.

Homberg held several posts within the academy— head of the chemical laboratory after 1699, director (1701 and 1707), sous-director (1703 and 1709), and member of various committees. He was the mentor to several younger academicians, most notably Étienne-François Geoffroy. Homberg’s work and theory was highly influential in the early eighteenth century; for example, his ideas are often invoked in the writings of Hermann Boerhaave, Peter Shaw, and Pierre-Joseph Macquer as well as by Georg Ernst Stahl and others.

Contemporaneous accounts of Homberg agree on his friendly, good-natured personality, his generosity, sincere piety, and kindness. Elisabeth Charlotte, duchesse d’Orléans, held him in high regard, writing that “one is unable to get to know Homberg without esteeming him for his honest spirit; he is not at all befuddled as savants usually are, nor ponderous, nor lofty, but instead always merry” (Bodemann, 1891, vol. 2, p. 11). The duc de Saint-Simon avers that Homberg was “one of the greatest chemists of Europe, and one of the most honest men who ever lived; he was the most simple and the most solidly pious” (Saint-Simon, 1985, vol. 5, p. 742).

SUPPLEMENTARY BIBLIOGRAPHY

Bodemann, Eduard, ed. Aus der Briefe der Herzogin Elisabeth Charlotte von Orléans an die Kurfürstin Sophie von Hannover. 2 vols. Hannover, Germany, 1891.

Franckowiak, Rémi, and Luc Peterschmitt. “La chimie de Homberg: Une vérité certaine dans une physique contestable.” Early Science and Medicine 10 (2005): 65–90.

Holmes, Frederic L. “The Communal Context for ÉtienneFrançois Geoffroy’s Table des rapports.” Science in Context 9, no. 3 (1996): 289–311.

Principe, Lawrence M. “Wilhelm Homberg: Chymical Corpuscularianism and Chrysopoeia in the Early Eighteenth Century.” In Late Medieval and Early Modern Corpuscular Matter Theories, edited by Christoph Lüthy, John E. Murdoch, and William R. Newman, 535–556. Leiden, Netherlands, and Boston: Brill, 2001.

———. Wilhelm Homberg and the Transmutations of Chemistry at the Académie Royale des Sciences. Forthcoming, 2008.

Saint-Simon, Louis de Rouvroy, duc de. Mémoires. 8 vols. Edited by Yves Coirault. Paris: Gallimard, 1985.

Stroup, Alice. “Wilhelm Homberg and the Search for the Constituents of Plants at the 17th-Century Académie Royale des Sciences.” Ambix 26 (1979): 184–202.

Lawrence M. Principe