Homberg, Wilhelm or Guillaume

(b. Batavia, Java [now Jakarta, Indonesia], 3 January 1652; d. Paris, France, 24 September 1715)

chemistry.

Although Homberg’s greatest contribution was to introduce the new scientific chemistry to the French Academy of Sciences, his life resembled that of many alchemists. His father, Johann Homberg, was originally from Saxony; upon the loss of his property in the Thirty Years’ War he entered the service of the Dutch East India Company as a soldier. His mother, Barbe van Hedemard, had come to Java as the wife of a Dutch officer. Homberg, the second of four children, was made a corporal at the age of four; but his education was neglected because it was thought impossible for a European child to study in a tropical climate. When his father took the family to Amsterdam, Homberg showed great intellectual aptitude; he was soon studying law at Jena and Leipzig and was accepted as a practicing lawyer at Magdeburg in 1674.

Here he discovered the fascination of botany and astronomy. Here too he met Otto von Guericke, who introduced him to experimental physics and is said to have taught him the secret of the hygrometric toy in which a figure appears in fine weather and withdraws in rainy weather. Homberg later traded this secret to Johann Kunckel in return for that of the preparation of phosphorus.

In pursuit of scientific knowledge Homberg traveled to Padua (where he studied medicine), Bologna (where he interested himself in the mysteriously phosphorescent “Bononian stone”), Rome, France, England (where he apparently worked with Boyle), and Holland. He took the M.D. degree at Wittenberg, investigated the German preparations of phosphorus and mining techniques, and worked in the chemical laboratory established by the king of Sweden. He then went to Paris, where he was supported by Colbert; and in 1682 he was converted to Catholicism. Colbert’s death in 1683 left Homberg without resources, his father having disowned him both for his change of religion and for his wandering life. The gift of an ingot of “alchemical gold” by a friend is said to have permitted him to go to Rome, where he practiced as a chemist and physician while maintaining contact with French circles. The Abbe Bignon appointed him a member of the Royal Academy of Sciences in 1691. The rest of his life was spent in Paris, and his work was all done within the framework of the Academy. He was also associated with Philippe II, duke of Orléans, who in 1702 gave him a pension and laboratory, and bought for him a burning mirror made by Tschirnhausen. In 1708 Homberg married Marguerite-Angélique, daughter of the physician and botanist Denis Dodart.

In contrast with the romanticism of his external life, Homberg’s intellectual existence was rational, empirical, and scientific. He had wide experience in experimental physics, publishing on the breaking of Prince Rupert’s drops, the production of frictional electricity, and the expansion and contraction of substances by heat and cold. (The table of the variation of specific gravities with temperature, published in the Mémoires of the Academy in 1699, was used by later writers.) Like his mentor Boyle, Homberg carried the point of view of an experimental yet mechanical philosopher into the practice of chemistry and encouraged French chemists to follow. This is shown in his work at meetings of the Academy, as revealed in its Registres de physique (1692–1715). For example, he exploded the validity of the analyses of plants into their supposed elements or principles (salt, oil, spirit, etc.) and introduced the notion of analysis into “simple substances” (recognizable and stable chemical entities) which made possible eighteenth-century French analytical chemistry.

In his “Essais de chimie” (1702–1710) Homberg dicussed the general concept of principles or elements and concluded that salt, not all to be found in all substances. Thus, he thought that mercury was present in metallic ores and metals but not in “fossils” (nonmetallic minerals) and salts, while organic substances had a set of principles different from those of inorganic substances. This was a step toward the modern definition of an element. Probably his most important work was on the strength of acid and the quantity of acid required to neutralize a given quantity of alkali (two papers published in 1699 and 1700). Homberg recognized that different alkalies neutralized the same acid in different proportions but believed that the relative strengths of two acids could be determined by using the same alkali in each case. He treated the question of neutralization (or dissolvability, as he called it) in quite quantitative fashion, showing that if an alkaline salt were treated with an acid, the gain in weight of the salt was an indication of the amount of acid absorbed. He came to regard specific gravity as a true indication of acid strength. Although naturally unaware of the role of gases in acid-alkali neutralizations, Homberg nevertheless understood the fundaments of the process and thereby laid the foundation for an understanding of the nature of salts. In 1702, in his “Essai” on salt, he dicussed the replaceability of metals in solution, much as Newton later did in Query 31 of Opticks, although without any notion of attraction.

To his contemporaries, much of Homberg’s most interesting work lay in his dramatic quasi-alchemical explorations. In 1692 he he published a method for making “the tree of Diana” a spectacular form of crystallization of silver salts. He published experiements on varuious forms of “phosphorus", including his own discovery of the luminous and explosive properties of calcium chlorate. With his burning glass he performed experiments on calcination, fusibility, and volatility. Homberg also published on pneumatics, botany, and zoology. He was one of the leading scientific spirits of the reformed Royal Academy of Sciences and highly influential in developing its course of research in the experimental sciences.

BIBLIOGRAPHY

I. Original Works. All Homberg’s work was published in the form p papers and essays (well over 70 in all) in the Histories et meämoires de L’Acadeämie royal des sceiences (1692–1714). A list of 53 of these. mainly on chemical subjects, is at the end of his biography in the Nouvelle biographie geéneérale. Among the most important are “Diverses experiences du phosphore” (1692), “Observation sur la quantite exacts des sels volatils acides contenus dan sles différents sprits acides” (1692), (1699), “Observations sur la quantite d’acide absorbéss par les alcalis terreux” (1700), and “Essais de chimie” (1702, 1705, 1706, 1710), on the principles of salt, sulfur, and mercury. His contributions to the daily activittes of the Academy are preserved in the archives of the French Academy of Sciences.

II. Secondary Literature. The chief source for Homberg’s biography is the eäloge by Bernard le Bovier de Fontenelle published in Histories et meämoires de l’Académic, royale des sciences (1715), repr. in Oeuvres de Fontenelle, éloges, I (Paris, 1825), 307–319. There are good appraisals of his work in F. Hoefer, Histoire de la chimie, II (paris, 1866), 298–304; and J. R. Pratington, History of Chemistry, III (London, 1962), 42–47. The best analysis of his contribution to chemical theory is in Helene Metzger, Les doctrines chimiques en France (Paris, 1923), passim, see esp. pp. 340 ff.

Marie Boas Hall