1911 Encyclopædia Britannica/Fluorene

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FLUORENE (α-diphenylene methane), C13H10 or (C6H4)2CH2, a hydrocarbon found in coal-tar. It is obtained from the higher boiling fractions, after separation of naphthalene and anthracene, by fractional distillation, the portion boiling between 290–340° C. being taken. The fluorene is separated from this by placing it in a freezing mixture, and is then redistilled or crystallized from glacial acetic acid, or purified by means of its picrate. It may be prepared by distilling diphenylene ketone over zinc dust, or by heating it with hydriodic acid and phosphorus to 150–160° C.; and also by passing the vapour of diphenyl methane through a red hot tube. It crystallizes in colourless plates, possessing a violet fluorescence, melting at 112–113° and boiling at 293–295° C. By oxidation with chromic acid in glacial acetic acid solution, it is converted into diphenylene ketone (C6H4)2·CO; whilst on heating with hydriodic acid and phosphorus to 250–260° C. it gives a hydro derivative of composition C18H22.