Mitscherlich, Eilhard

Schiitt, H.-W. (1997) Eilhard Mitscherlich, Prince of Prussian Chemistry (American Chemical Society and the Chemical Heritage Foundation). 

A striking example of the importance of narrowing the focus in research, which is what the concept of the parepisteme really implies, is the episode (retailed in Chapter 3, Section 3.1.1) of Eilhard Mitscherlich s research, in 1818, on the crystal forms of potassium phosphate and potassium arsenate, which led him, quite unexpectedly, to the discovery of isomorphism in crystal species and that, in turn, provided heavyweight evidence in favour of the then disputed atomic hypothesis. As so often happens, the general insight comes from the highly specific observation. 

On February 24, 1829, Berzelius wrote to Eilhard Mitscherlich, "Wollaston s death grieves me. His specifications for making platina pliable were circulated at the same time as the news of his death. As I got iridium to cohere in an analogous manner, I was struck all the more by his simple method, went out into the laboratory, where I had a wet filter with platina on it, partly washed, which I pressed in a vice, dried, and ignited over a spirit lamp in a small platina crucible, and got it so coherent that it could no longer be broken with the fingers and could easily be cold-hammered. That s as far as I have yet gone. That was ten minutes work, then I had to let it wait for a better time (83). 

G. B. Kauffman, I. Bernal and H.-W. Schiitt, Overlooked opportunities in stereochemistry, Part IV. Eilhard Mitscherlich s near discovery of conglomerate crystallization on the sesquicentennial of Pasteur s resolution of sodium ammonium racemate , Enantiomer, 1999, 4, 33—45. 

The German chemist Eilhard Mitscherlich published a note in 1844 in the Reports of the Academy of Science on the subject of the tartrate and paratartrate of sodium and ammonia. The importance of this note is now acknowledged by Pasteur. 

Eilhard Mitscherlich in 1844 reported that solutions of commercial tartaric acid rotated the plane of polarized light in a clockwise manner, while solutions of racemic acid had no effect on plane-polarized light. This finding was surprising because the chemical formulae of these two acids are the same, HOOC-CH(OH)-CH(OH)-COOH, and their crystals appeared identical. Mitscherlich posed this problem as Mitscherlich s riddle. ... 

The phenomenon of polymorphism was noted by Martin Heinrich Klaproth °i in 1798, when he proposed that the minerals calcite and aragonite must have the same chemical composition, CaCOa. Calcite forms a rhombohedral uniaxial crystal and is the stable form under normal conditions, with a density of 2.71 g/ml. Its metastable polymorph, aragonite, is an orthorhombic biaxial crystal with a density of 2.94 g/ml. This work was continued by Louis Jacques Thernard, Jean Baptiste Biot, and Eilhard Mitscherlich. Mitscherlich, for example, reported on it in his studies of phosphates and arsenates. The transition from calcite to aragonite has been studied at different pressures. ... 

FIGURE 269. Statement 17 on pages 6 and 7 of Mendeleev s master s dissertation discusses the angles measured in crystals of related substances. The Periodic Law, published by Mendeleev in 1869, would explain the similarities between isomorphic crystals, first noted by Eilhard Mitscherlich some 40 years before Mendeleev s master s dissertation was published. (From The Roy G. Neville Historical Chemical Library, a collection in the Othmer Library, CHE)... 

Mitscherlich s law /mich-er-lik/ (law of isomorphism) The law stating that substances that crystallize in isomorphous forms (i.e. have identical crystalline forms and form mixed crystals) have similar chemical compositions. The law can be used to indicate the formulae of compounds. For instance, the fact that chromium(III) oxide is isomorphous with Fe203 and AI2O3 implies that its formula is Ct203. The law is named for the German chemist Eilhard Mitscherlich (1794-1863). 

I. Gesammelte Schriften von Eilhard Mitscherlich, Lebensbild, Briefwechsel und... 

The parent compound of the aromatics is benzene it was first discovered by Michael Faraday in 1825 in the condensed part of a lighting gas derived from whale oil and obtained some years later by Eilhard Mitscherlich by decarboxylation of benzoic acid (as calcium benzoate). The occurrence of benzene in coal tar was first described by August Wilhelm v. Hofmann in 1845. John Leigh had already demonstrated to the British Natural Research Conference in 1842, that benzene is present in coal tar this claim was not immediately published, however. Even before the discovery of benzene, Ferdinand Runge had found aniline and phenol in coal tar in 1834. 

After Michael Faraday discovered benzene in the lighting gas from whale oil in 1825, Eilhard Mitscherlich established in 1834 that the summation formula for benzene, which he had produced by decarboxylation of benzoic acid, is C6H6. 

Nitrobenzene was first obtained by Eilhard Mitscherlich in 1834, by nitration of benzene. In England in 1847, its production from coal-tar benzene was patented and the technology developed by Charles B.Mansfield manufacture began in France in 1848. 

Eilhard Mitscherlich Prince of Prussian Chemistry Hans-Werner Schutt... 

Aromaticity is one of the most fascinating popular qualitative chemical concepts in chemistry Michael Faraday isolated benzene by distillation in 1825. He noticed that although benzene is an unsaturated compound with H C 1 1 it is much less reactive than the related unsaturated aliphatic compounds. Moreover, it undergoes substitution reactions rather than addition reactions exhibited by alkenes and alkynes. Eilhard Mitscherlich synthesized benzene by heating benzoic acid with lime. 

Two important discoveries were used by Berzelius in revising his atomic weight values before publishing his final table in 1826. The first was the law of isomorphism, which was published in 1820 by the German Eilhard Mitscherlich... 

In 1819 the German chemist Eilhard Mitscherlich (1794-1863) discovered isomorphism, the existence of different crystalline substances with essentially the same crystal form, and suggested his rule of isomorphism, which states that isomorphous crystals have similar chemical formulas. 

The compound we know as benzene was first isolated in 1825 by Michael Faraday. He extracted it from the liquid residue obtained after heating whale oil under pressure to produce the gas then being used in gas lamps. In 1834, Eilhard Mitscherlich correctly determined the molecular formula of Faraday s compound and named it benzin... 

Anneliese Greiner and Hermann Klare, eds., Chemiker iiber Chemiker Wahlvorschldge zur Aufnahme von Chemikern in die Berliner Akademie 1822-1925 von Eilhard Mitscherlich bis MaxBodenstein (Berlin Akademie-Verlag, 1986), 133. 

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