Georg Ernst Stahl (22 October 1659 – 24 May 1734) was a German chemist, physician and philosopher. He was a supporter of vitalism, and until the late 18th century his works on phlogiston were accepted as an explanation for chemical processes.

Raised as a son to a Lutheran pastor, he was brought up in a very pious and religious household. From an early age he expressed profound interest in chemistry, by age 15 mastering a set of university lecture notes on chemistry and eventually a difficult treatise by Johann Kunckel. He had two wives, who both died from puerperal fever in 1696 and 1706. He also had a son Johnathan and a daughter who died in 1708. He was raised in Pietism, which influenced his viewpoints on the world. His interests in chemistry were due to the influence a professor of medicine, Jacob Barner, and a chemist, Johann Kunckel von Löwenstjern. In 1694, he held the chair of medicine at the University of Halle. From 1715 until his death, he was the physician and counselor to King Friedrich Wilhelm I of Prussia and in charge of Berlin's Medical Board. His main argument on living things was that there is an agent responsible for delaying this decomposition of living things and that agent is the anima or soul of the living organism. The anima controls all of the physical processes that happen in the body. It not only just controls the mechanical aspects of it but the direction and goals of them too. Also, during the first part of the 18th century, Stahl's ideas on the non-physical part of the body were disregarded while his mechanistic ideas on the body were accepted in the works of Boerhaave and Hoffmann.

Tonic motion

As a physician, Stahl worked with patients and focused on the soul, or anima, as well as blood circulation and tonic motion. Anima was a vital force that when working properly would allow the subject to be healthy; however, when malfunction of the anima occurred, so did illness. Tonic motion, to Stahl, involved the contracting and relaxing movements of the body tissue in order to serve the three main purposes. Tonic motion helped explain how animals produce heat and how fevers were caused. In Stahl's 1692 dissertation, De motu tonico vitali, Stahl explains his theory of tonic motion and how it is connected to blood flow within a subject, without citing William Harvey's blood flow and circulation theories, which lacked an explanation of irregular blood flow. Also within the dissertation, 'practitioners' are mentioned as users of his theory of tonic motion.

Stahl's theory of tonic motion was about the muscle tone of the circulatory system. During his work at Halle, Stahl oversaw patients experiencing headaches and nosebleeds. Tonic motion explained these phenomena as blood needed a natural or artificial path to flow when a part of the body is obstructed, injured, or swollen. Stahl also experimented with menstruation, finding that bloodletting in an upper portion of the body would relieve bleeding during the period. During the next period, the wound would experience pain and swelling, which would only be relieved by an opening in the foot. He also followed this procedure as a treatment for amenorrhoea.

Chemistry

The best of Stahl's work in chemistry was done while he was a professor at Halle. Just like medicine, he believed that chemistry could not be reduced to mechanistic views. Although he believed in atoms, he did not believe that atomic theories were enough to describe the chemical processes that goes on. He believed that atoms could not be isolated individually and that they join to form elements. He took an empirical approach when establishing his descriptions of chemistry. Stahl, influenced by Becher's work, developed his theory of phlogiston. Phlogiston theory did not have any experimental basis before Stahl worked with metals and various other substances in order separate phlogiston from them. Stahl proposed that metals were made of calx, or ash, and phlogiston and that once a metal is heated, the phlogiston leaves only the calx within the substance. He was able to make the theory applicable to chemistry as it was one of the first unifying theories in the discipline. Phlogiston provided an explanation of various chemical phenomena and encouraged the chemists of the time to rationally work with the theory to explore more of the subject. This theory was later replaced by Antoine-Laurent Lavoisier's theory of oxidation and caloric theory.

Family

Georg Ernst Stahl was married three times. His first wife was Catharina Margaretha Miculcin (1668–1696). After the death of his first wife in 1696, he married Barbara Eleonora Tentzel (1686–1706) on 12 February 1705, daughter of the Electoral Brandenburg Tax Council in Halle (Saale) Johann Christian Tentzel. After the death of his second wife in 1706, on 26 February 1711 he married Regina Elisabeth Wesener (1683–1730), daughter of the city doctor in Halle, Wolfgang Christoph Wesener (1640–1706).

He had nine children:

  • Johann August Stahl (b. 1694)
  • Christina Catharina Sophia Stahl (b. 1696)
  • Eleonora Stahl (1706–1708)
  • Regina Ernestina Stahl (b. 1712), married Johann August Arends (1703–1747).
  • (1713–1772), in 1741 married Johanna Elisabeth Schrader (1725–1763), daughter of pharmacist (1683–1744), had nine children.
  • Johann Christoph Stahl (b. 1714)
  • Sophie Dorothea Stahl (b. 1716)
  • Catharina Charlotta Louisa Stahl (1717–1784), in 1735 married royal Prussian Court Councillor and Professor university (1704–1772), had ten children, including (1739–1797).
  • Sophia Rosina Stahl (1722–1801), in 1740 married Hofkriminalrat and Postrat in Berlin Johann Georg Buchholtz (1714–1771).

Works

thumb|De lapide manati, 1710

  • Zymotechnia fundamentalis (1697)
  • Disquisitio de mechanismi et organismi diversitate (1706)
  • Paraenesis, ad aliena a medica doctrine arcendum (1706)
  • De vera diversitate corporis mixti et vivi (1706)
  • Theoria medica vera (1708)
  • Georgii Ernesti Stahlii opusculum chymico-physico-medicum : seu schediasmatum, a pluribus annis variis occasionibus in publicum emissorum nunc quadantenus etiam auctorum et deficientibus passim exemplaribus in unum volumen iam collectorum, fasciculus publicae luci redditus / Praemißa praefationis loco authoris epistola ad Michaelem Alberti (1715) Digital edition by the University and State Library Düsseldorf
  • Specimen Beccherianum (1718)