255 
did not know examples from literature in which diazotisation in 
this way proceeds quantitatively, we have subjected his experiments 
to an examination. To this end we worked as follows : 
100 ee. */,5, N sulphanilie acid sol. were poured into a beaker, 
placed in melting ice. As a second liquid, a nitrite sol. was used, 
containing */,,,, gram-molecule NaNO, (controlled with KMnO,) per 
400 ee. Before the experiment was made both solutions were cooled 
to 0°; then they were mixed while being well stirred. After 90 minutes 
(TassiLLy finds 100 °/, amine inverted after 20 minutes already) we 
coupled 5 ec. of this solution with 5 ce. of the ScHArrnr’s salt 
solution as used by him. Then as much strong HCl was poured 
into the reaction vessel as was necessary to liberate the nitrous 
acid from the nitrite and to bind the amine. After 20 ‘minutes we 
again took 5 ee. and coupled them with the same ScHAFFER’s salt 
solution (5 ee). After 12 hours the colour was compared with that 
of experiment n°. 1 in the colorimeter (see next page); the colours 
were related approximately as 30: 100. So we may conclude that 
the diazotisation when HCI is absent, does not become complete. 
It is evident that because of this, his conelusions sub 3 and 4, 
based on his researches on sulphanilic acid have no great value. 
We see from the preceding that from the researches made till 
now, nothing can be deduced but that the diazotisation reaction 
proceeds quickly and is bimolecular. In spite of the -imperfections 
of Tassi_iy’s research, we thought we could follow his method if 
only we took care: 
1. that the diazotisations were executed under entirely equal 
circumstances. To this end care was taken that at all times a con- 
siderable excess of HCI, in every case the same, was present. 
2. that when adding ScHArrer’s salt, a sufficient quantity of 
alkali was present in order to stop the diazotisation with certainty. 
3. that the determinations were accurately performed. 
We attained this by making use of a simple colorimeter accord- 
ing to Worrr, after having ascertained that the resulting azo dyes 
complied with Brrr’s law in the dilutions used by us and that the 
estimations were not disturbed by the presence of amine not yet 
inverted. We proceeded as follows: 
In a beaker, placed in melting ice 100 ec. '/,,, N. amine hydro- 
chloride were poured, containing at the same time 5 c.c. HCI (spec. 
gr. 1.19) per Liter, in order to prevent the formation of diazo amide 
compounds and to set free HNO,. As the second liquid a nitrite 
solution was taken, which contained ‘/,,,, gram. mol. NaNO in 
400 c.c. (controlled with KMnQ,). Before the beginning of the experi- 
