<unk>  refers to any of three isomeric compounds, C6H4(NO2)2, made from a mixture of nitric acid, sulfuric acid, and heated benzene and used in celluloid manufacture, in dyes, and in organic synthesis.
Dinitrobenzene
Toluene
Coal tar
Benzene
Vinyl chloride
Nitrazine
Methylene diphenyl diisocyanate
Trichloroethylene