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MATH PUZZLE: Can you replace...

MATH PUZZLE: Can you replace the question mark with a number?

Correct answers: 113

The first user who solved this task is H Tav.

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Carl Graebe

Died 19 Jan 1927 at age 85 (born 24 Feb 1841).German organic chemist who, assisted by Carl Liebermann, synthesized (1868) the orange-red dye alizarin, which in the textile industry quickly supplanted the natural source of the dye from the madder plant root. Alizarin (dihydroscyanthraquinone) was recognized by Graebe and Liebermann, as a derivative of anthracene, a hydrocarbon contained in coal-tar. Also in 1868, they elaborated a method for preparing it commercially from anthracene. Upon this, one of the early German dyestuff products, arose rapidly a great chemical industry. Graebe also introduced the chemical terms "ortho," "meta," and "para," well known to organic chemistry students, which indicate the position of groups attached to a benzene ring.

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