What is "phenazine"

n. (context chemistry English) any of a class of aromatic tricyclic heterocycles used to make dyestuffs

Phenazine (CHN or CHNCH), also called azophenylene, dibenzo-p-diazine, dibenzopyrazine, and acridizine, is a dibenzo annulated pyrazine and the parent substance of many dyestuffs, such as the toluylene red, indulines and safranines (and the closely related eurhodines). Phenazine crystallizes in yellow needles, which are only sparingly soluble in alcohol. Sulfuric acid dissolves it, forming a deep-red solution.