Purpurine Benzo

The rate of coagulation of night blue examined by Biltz and Steiner Zeit, Phys. Ohem, LXXili. 607, 1910) and of benzo-purpurin (Biltz and v, Vegesack, Zeit. Phys. Ghem. lxxiii. 500, 1910) likewise appear to conform reasonably closely to a reaction of the autocatalytic variety. 

If o-tolidine is used in place of benzidine, the dyestuff formed is Benzo-purpurin 4B. (D.R.P., 84893.)... 

Benzo purpurin.— Tolidine is di-methyl benzidine, that is it bears the same relation to toluene and ortho-toluidine that benzidine does to benzene and aniline. When this is diazotized and the tetrazonium salt coupled with sodium naphthionate the disazo compound resulting is a dye known as benzopmpurin 4B, which is also a substantive dye of a red color. 

In 1886 an important development took place in the azo colotir-industry. This was based on an observation made by Griess (pat. 1884), that certain azo-dyestuffs derived from benzidine were capable of dyeing vegetable fibres without mordant. As members of this class of dyestuffs, which are very numerous, may be mentioned chrysamine, congo red, benzo-purpurine, c. 

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