Tri-amino Azo Benzene

The important tri-amino azo compound is the one in which two amino groups are in one ring, ortho and para to the azo group and one amino group meta to the azo group in the other ring. The constitution of the compound is proven by its preparation from meta-phenylene di-amine, we/a-di-amino benzene. This is diazotized so that only one 

When the diazotization of the meta phenylene diamine is carried further so that both amino groups are diazotized a double diazo compound or tetrazo compound is obtained and this couples with two molecules of meta-phenylene diamine yielding a double azo or dis-azo compound. 

Bismarck Brown.—The dis-azo compound obtained meta-diamino benzene dis-azo benzene meta-di-amino benzene is a dye known as Bismark brown, though the dye is probably a mixture of the dis-azo compound and tri-amino azo benzene. With the exception of aniline yellow or amino azo benzene it was the first azo dye to be made. It was first prepared by Martins in 1864, and first made as a dye in 1866. 

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