University of Marburg, Marburg, Hessen, Germany
Juncker was a student of philosophy at the University of Marburg in 1696.
University of Halle, Halle, Germany
Juncker went to Halle in 1697, where he studied theology and followed a program in literature under the classical scholar Christopher Cellarius.
Juncker received his primary education in Giessen. He was a student of philosophy at the University of Marburg in 1696 and then went to Halle, where he studied theology under August Hermann Francke and followed a program in literature under the classical scholar Christopher Cellarius. Juncker taught in Halle from 1701 to 1707 and then left to study medicine in Erfurt, where he received his Doctor of Medicine degree in 1717.
In 1716 Juncker returned to Halle as physician to the Royal Pedagogical Institute and Orphanage that Francke had founded, beginning a distinguished career in that city which culminated in his appointment to the chair of medicine at Halle in 1729 and ultimately his selection as Prussian privy councillor. Juncker also held the position of professor of medicine at Halle from June 29, 1729 until his death on October 25, 1759.
The University of Halle, a Pietistic stronghold, possessed two of the outstanding chemical and medical theorists of the early eighteenth century, Georg Ernst Stahl and Friedrich Hoffmann. Juncker benefited from his close association with these brilliant colleagues and became one of Stahl’s most gifted and prominent disciples. When Stahl went to Berlin in 1716 Juncker corresponded with him and published numerous dissertations and books that expounded and developed Stahlian ideas in chemistry and medicine. He reiterated Stahl’s admonition to keep these two disciplines distinct, arguing that chemical theory had little to offer medical practice at that time. His medical treatises censured both the iatrochemical and iatromathematical traditions and elaborated Stahl’s vitalist theories. Juncker and another colleague in Halle, Michael Alberti, disseminated Stahlian vitalism throughout Europe and assisted in establishing an alternative in medical thought to the mechanical theories of Boerhaave.
Juncker’s most important chemical text was the Conspectus chemiae theoretico-practicae (1730), a systematic exposition of the ideas and experiments of Becher and Stahl. By providing a critical and coherent treatment of Stahl’s studies on chemical composition and reaction, the Conspectus offered a more intelligible version of Stahl’s work that gave it a greater audience.
Juncker was a leader in the Pietist reform movement as it applied to medicine.
Juncker stressed the necessity for grounding chemical theory in accurate and extensive experimental data and, after establishing the definition, aims, and utility of chemistry, applied the Becher-Stahl hierarchy of matter as the fundamental schema for chemical explanation. He adopted Stahl’s ideas on the nature of the elements, including phlogiston (which he emphasized was a material principle and not merely the property of burning) and, like Stahl, denied air a chemically active role, maintaining that it acted only as a physical instrument during reactions. Thus in combustion and calcination, air served to expedite the release of phlogiston from compounds, without itself entering into any chemical combination.
Juncker was married three times. His first marriage was in 1707 to Charlotte Sophie von Waldeck und Pyrmont, the daughter of Count Christian Ludwig. His second marriage was in 1725 to Johanna Elisabeth Lichtenberg, the daughter of Johann Philipp Lichtenberg, the administrator of Jagersburg. Of this marriage, one daughter, Philippine Louise, survived, marrying the physician Peter Nicolai Neugart in April 1743. Juncker's third marriage was on April 17, 1727, to Christiane Eleonore von Bomsdorf, the daughter of the Saxon Oberst Phillip Wilhelm von Bamsdorff. The son of this marriage was the physician Friedrich Christian Juncker who also became a Halle professor of medicine.