RETENE (methyl isopropyl phenanthrene), C18H  ,8, a hydro-carbon present in the coal-tar fraction, boiling above 36o° C.; it also occurs in the tars obtained by the distillation of resinous woods . It crystallizes in large plates, which melt at 98.5° C. and boil at 390° C . It is readily soluble in warm ether and in hot glacial acetic acid . Sodium and boiling amyl alcohol reduce it to a tetrahydroretene, whilst if it be heated with phosphorus and hydriodic acid to 26o° C. a dodecahydride is formed . Chromic acid oxidizes it to retene quinone, phthalic acid and acetic acid . It forms a picrate which melts at 123–124° C .