(methyl isopropyl phenanthrene), CisHis, a hydrocarbon present in the coal-tar fraction, boiling above 360° 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, - t whilst if it be heated with phosphorus and hydriodic acid to 260° 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.