“ With picric acid it forms a sparingly soluble picrate, which melts at 145° C. On the condition of phenanthrene in alcoholic solution see R. Behrend, Zeit. phys. Chem., 1892, 9, p. 405; 10, p. 265. Chromic acid oxidizes phenanthrene, first to phenanthiene-quinone, and then to diphenic acid, HO2C·C6H4·C6H4·CO2H.
Phenanthrene-quinone, [C6H4] 2 [CO] 2, crystallizes in orange needles which melt at 198° C. It possesses the characteristic properties of a diketone, forming crystalline derivatives with sodium bisulphite and a dioxime with hydroxylamine. It is non-volatile in steam, and is odourless. ”