FLUORENE (a-diphenylene methane), C13H16  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 1 50—16o° 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 (CsH4)z•CO; whilst on heating with hydriodic acid and phosphorus to 250—260° C. it gives a hydro derivative of composition C13H22 .