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Mitscherlich, Eilhardt

formulas chemistry found berlin

[mit sherleekh] (1794–1863) German chemist and mineralogist: discovered law of isomorphism.

Mitscherlich’s youthful enthusiasm was the Persian language, which he studied at Heidelberg and Paris in the hope of visiting Persia as a diplomat. When this appeared impossible he decided to study medicine, with the intention of travelling as a physician. To begin, he studied science in Göttingen; and was soon so attracted by chemistry that he gave up the idea of visiting Persia. He moved to Berlin in 1818 to study chemistry and soon noticed that potassium phosphate and potassium arsenate form nearly identical crystals. He went to Stockholm to work with for 2 years, continuing to measure crystal angles and forms; where these were closely similar in different compounds, he described them as ‘isomorphous’. His law of isomorphism states that isomorphous crystals have similar chemical formulas. For example, he showed that the manganates, chromates, sulphates and selenates are isomorphous; from this the formula of the newly discovered selenates could be deduced (as the formulas of the first three were known) and from the formula the relative atomic mass of selenium was found by analysis. From 1825 Mitscherlich was professor of chemistry at Berlin.

Berzelius and others found the law useful in deducing formulas, and therefore relative atomic masses, for several elements and for correcting earlier erroneous formulas. Mitscherlich continued his work on crystallography; he found that some substances (eg S) can crystallize in two forms (dimorphism) or even more (polymorphism). From 1825 Mitscherlich was professor in Berlin. As well as crystallography, he worked on organic chemistry, microbiology, geology and catalysis. He first made benzene (and named it Benzin ) by heating calcium benzoate; and also nitrobenzene, azobenzene and benzenesulphonic acid. He helped his youngest son develop an important industrial process for obtaining cellulose from wood pulp by treatment with hot aqueous calcium hydrogen sulphite solution.

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