188 REPORT— 1902. 



The existence of analogous intermediate diazoamino- compounds and 

 diazohydroxy-derivatives in the commercial azo-colouring matters, has been 

 recently demonstrated by Vaubel.'^ 



Although aniline and other benzenoid primary amines give rise to 

 diazoamines when treated with diazonium salts, their dialkyl derivatives 

 containing a free para-position with respect to nitrogen readily furnish 

 azo-compounds of the methyl orange type. The formation of these 

 colouring matters is governed by the following laws : ^ 



(i) The velocity of formation of the aminoazo- compound depends only 

 on the nature of the reagents and not on the concentration. 



(ii) In coupling the hydrochloride of a tertiary base with diazobenzene 

 sulphonic acid, the interaction occurs between the diazo-compound and the 

 base set free by the hydrolytic dissociation of its salt. 



These laws are deduced from the following facts : — The concentration 

 of the hydrochloride of the base or the diazo-compound has no influence 

 on the velocity of condensation. Excess of hydrochloric acid lessens the 

 velocity. The formation of methyl orange or the corresponding ethylated 

 colouring matter, 



N, -, 



Co H / I + H.CgH^NR, -> HSOg.CgH.No. CgH.NRj, 



when carried out in the presence of different acids {e.f/., acetic, mono-, di-, 

 and tri-chloracetic acids and hydrochloric acid), takes place most rapidly 

 with the weakest acid, the velocity decreasing as the affinity constant of 

 the acid increases. 



Azo-derivatives of the aromatic 7neta-diammea, although amongst the 

 oldest of the colouring matters, are still manufactured on a large scale for 

 the use of the dyer. Bismarck brown, which was prepared even before 

 the exact nature of thediazo-reaction had been elucidated, is still employed 

 in the arts, and the precise composition of the commercial product has only 

 recently been established by the researches of Tauber.^ 



Chrysoidine, first introduced by Witt,'* also maintains its position 

 against the newer dyestufi's. Its homologues and substitution products 

 may be readily and quantitatively prepared from any of the derivatives 

 of »?i-phenylenediamine, providing that these substances contain at 

 least one free para-position with respect to an amino-radicle. If this 

 condition is not fulfilled the production of an azo-compound, although 

 still possible if the diamine contains a free ortho-position with respect to 

 nitrogen, is nevertheless very considerably hindered. The formation of 

 azo-derivatives fi'om symmetrically disubstituted primary ?M-diamines has 

 been demonstrated,'' but the reaction 



CeHaN.Cl + CHsCOjNa = 



* 2eit. Farhen. Textilclwm., 1902, 1, 3. 



- Goldschmidt and Merz, Ber., 1897, 30, 670 and 2075 

 ' Ber., 1897, 30, 2111, 2899 ; 1900, 33, 2116 



* Ber., 1877, 10, 656. 



* Morgan, Trans., 1902, 81, 86. 



