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Stahl, Georg Ernst

theory medicine phlogiston oxidation

[shtahl] (1660–1734) German chemist and physician; developed phlogiston theory of combustion.

A clergyman’s son, Stahl trained in medicine at Jena and later taught medicine and chemistry. He took a theory of combustion due to J J Becher (1635–82) and developed it well enough to dominate chemical theory for a century. The theory was that when a substance burned it was losing ‘phlogiston’. This was a principle of fire, perhaps akin to heat; and the idea was used to explain what we now call the oxidation of metals and the reduction of ores to metal. To account for the observed weight changes, phlogiston had to have negative weight. (Later, thought hydrogen might be pure phlogiston.) The theory was erroneous but not ludicrous. It could be made to account for a range of chemical reactions in a consistent way, and it pointed to further experiments. It was displaced, but not easily, from chemistry by work on oxygen, oxidation and reduction.

In medicine, Stahl’s best work was on mental illness. He was one of the first to see that some mental states are of physical origin, while others are functional; and he recognized the influence of the body on the mind and vice versa .

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Read more: Stahl, Georg Ernst - Theory, Phlogiston, Medicine, and Mental - JRank Articles http://encyclopedia.jrank.org/articles/pages/3608/Stahl-Georg-Ernst.html#ixzz2iLCpQ1W5