493 
more acid yellow. From these solutions, however, it always passes 
into the alcohol layer with a violet colour. The only explanation 
we can give is this, that the dye adds an H-ion to its 2-valent N- 
atoms. These additive products might then be blue, green, or yellow, 
the non-dissociated salt, however, violet. In the alcohol layer the 
H-ion concentration is much less than in the aqueous layer and so 
these additive products are formed with more difficulty. By a large 
excess of HCl the upper layer turns green also. The green solutions 
also regain their violet colour by strong dilution: the added hydrogen 
ions are again split off by dilution. 
“Patent blue” exaibits a similar behaviour ; a very little acid causes 
the concentration in the alcohol layer to increase, on addition of more 
acid it again decreases, while the aqueous layer turns first green 
and afterwards yellow. When the aqueous layer is already yellow, 
the alcohol layer is still green. 
The influence of acid and base was investigated quantitatively 
with methylene blue, quinoline-yellow and fuchsine. 
From table 1, 2 and 3; 6—7; 14, 15 and 16 we notice that with a 
large excess of acid or base the course of the division curve is quite 
analogous to that in the neutral solution. 
The influence of increasing quantities of acid or base is shown in 
the following table where in the first column is indicated the number 
of equivalents of acid or base in solution with one equivalent of 
colouring matter. The total quantity of dyestuff taken was always 
the <samey =. © 
DAB Ee 
Methylene blue D with Cy Cale. ier 
very much acid | 130 | 140 | 1.08 
8 eq. acid 140 | 120 | 0.86 
Ay pk | geo" | ',). 80: ly O50 
Bs ef PO MO IE 
ove hea 170 10 | 0.41 
neutral 170 | 70 | 0.41 
0.8 eq. KOH ee 170.) 9.10). | 0.44 
Le ne | 150 86 | 0.57 
ben ee | 1.25 
Hier oy | 90 | 300 | gana 
| | 
