Carbazole (molecular-type c12h9n) is a polycyclic nitrogen-containing heterocyclic organic matter, its structure similar to the one of the carbon atom replaced with nitrogen, so also known as nitrogen. Carbazole is a colorless crystal, from coal tar, can also be artificially synthesized. It is a very weak alkali, soluble in acetone, benzene or alcohol, insoluble in water, is synthetic dyestuffs (such as vulcanized VAT Blue Rx), plastic (such as poly-N-vinyl carbazole) and other raw materials. Carbazole exposure to ultraviolet light presents strong fluorescent and long phosphorescence, which can be used as a reagent for lignin, sugar and formaldehyde.