ON OUR PRESENT KNOWLEDQE OF AROMATIC DIAZO-COMPOUNDS. 203 



If this hypothesis is not accepted, then it must be assumed that a 

 quaternary ammonium hydroxide, having the functions of a strong base, 

 is also capable of behaving as an acid and yielding an alkali salt. The dia- 

 zonium hydroxide derived from anjsidine, for example, is a base com- 

 parable in strength with the alkalies, and yet it gives rise to a stable potassium 

 derivative,^ which, according to the alternative theory, has the formula 



OCH3.CGH4.N.OK 



N 



There are, however, absolutely no other examples of strong alkalies 

 behaving in this way. 



On the other hand, the hypothesis based on the change of configuration 

 due to the labile nature of the diazonium hydroxides, brings these bases 

 into line with other quaternary ammonium derivatives. It is well known 

 that almost all the quaternary ammonium hydroxides, excepting those in 

 which the nitrogen is attached to four fully saturated hydrocarbon 

 radicles, are unstable, and pass into substances in which the hydroxyl 

 group is no longer attached to the aminic nitrogen. This alteration is 

 noticed in the bases of the rosaniline, pyridine, and aci'idine series ; the 

 transformations taking place in each case being indicated by the following 

 diagrams : — 



V III 



>C:CcH4:NH20H -» >C(OH).C6H4.NH2 



=CH. V -CH(OHV III 



2)NR.0H -* >NIl 



— CH^ =CH/ 



/CH. .CH(OHk 



R< I >R -^ EC >R 



NROH ^^ ^ 



V III 



R.N.OH -► R.:N : N.OH 



N 

 Ammonium derivatives. Pseudo-ammonium derivatives. 



According to this generalisation the sy?i-diazo-hydroxides are to be 

 regarded as pseudo-diazonium derivatives.^ 



Solid Diazonium Halides. — The unstable character of certain dia- 

 zonium halides seems to be connected in some way with their colour, the 

 most highly coloured salts being very explosive. These coloured salts 

 are found to give colourless solutions, in which the salt is undoubtedly in 

 the form of a diazonium compound. The appearance of colour in the solid 

 state is considered to be due to the formation of a certain amount of 

 ^yw-diazo- derivative, in accordance with the condition of equilibrium : — 



R.N.X -> RN 



<- II 



N XN 



» Ber., 1900, 33, 2158. Ber., 1899, 33, 3109 ; 1900, 33, 278, 



