251 
up with water to 100 c.c. Simultaneously he brought in one of the 
cylinders 1 c.c. of a 0.001 N. nitrite solution and in the other four 
cylinders different quantities, accurately measured, of the liquid in 
the reaction vessel. The development of colour was then compared. 
However the colour does not appear instantaneously and therefore 
he did not compare the colour till after 15 minutes, though it still 
increases for some hours. 
It is clear, that in analysing each sample the diazotisation is not 
directly stopped; he allows the colour to develop in acid medium; 
the diazotisation continues and that with increased intensity because 
zine salts are still present, which notably accelerate the diazotisation’). 
Thus considerable errors are made. In this way it was of course 
impossible to Hanrzscu to examine the course of the diazotisation in 
the first stages of the reaction. At the same time it should be pointed 
out that his observations, as he diazotised in a weakly acidified 
solution will moreover be influenced by the formation of diazo-amino- 
compounds, which disturbance will vary according to the nature of 
the amine. 
The conclusions drawn by Hanrtzscu are as follows: 
1st. The rate of diazotisation is extremely great. 
2nd, Amines (aniline, p-toluidine, m-xylidine, p-bromaniline, p-nitro- 
aniline) are diazotised at equal rates (he ascribes differences to in- 
accuracies in his method) and he concludes from this that the 
presence of “negative” groups in the amine does not influence the 
rate of diazotisation. 
3rd, The rate of diazotisation is increased by the first excess of 
acid; however an excess of more than 1 mol. exersises no percei- 
vable influence on the velocity any more. 
4th, The diazotisation reaction is bimolecular and answers to the 
relation : 
1 wv 
i 
at a—w 
SCHUMANN °) has tried to affirm these results in another way. From 
the fall of electrical conductivity during the diazotisation, occasioned 
by the consumption of hydrochloric and of nitrous acid, he deduced 
the rate of the diazo reaction for some amines. In doing this he 
assumed the substituted aniline-hydrochlorides to have the same 
affinity constant, and the conductivity of the substituted diazonium 
salts to be the same*). Here some affinity constants follow: 
1) DLR. P. 171024, 172446, 175593. 
*) Ber. 33. 527. (1900). 
5) Ber. 28 1739 (1895). 
1% 
Proceedings Royal Acad. Amsterdam. Vol. X XIII. 
