490 
shown that different dyestuffs, particularly the basie and the acid ones, 
are dissolved molecularly in aqueous solution and, as shown by the 
conductivity of those solutions, are fairly strongly dissociated electro- 
lytically,. whereas the dissoviation in alcoholic solution is but trifling, 
we might expect that the transition into the alcohol layer would 
increase with a rise of the concentration. 
In order to explain this small exponent we can make different 
suggestions : 
1. The molecular size of the colouring matter is greater in the 
aqueous solution than ia the alcoholic one. 
This view finds support in the determinations of Krarrr’) on the 
lowering of the freezing point in aqueous and alcoholic solution. 
From these the following molecular weights are deduced: 
in water in alcohol theoretical 
Fuchsine ip ct 320— 344 SG 
Methyl violet 804—870 403—421 408 
Benzopurpurin = 8000 — 724 
Diamine blue 3430 — 999 
Hence, the two first basic dyestuffs would possess in water twice 
as great a molecular weight as in aleohol. These determinations, 
however, are not in harmony with the measurements of the con- 
ductivity power of most of the dyestuffs, dissolved as salts, which 
is about equal to that of a strongly dissociated binary electrolyte. 
2. The dyestuff (BS) in aqueous solution is partly dissociated 
hydrolytically. By the alcohol the neutral molecules are strongly 
absorbed, the ions are not. In the case of a basic dyestuff the mols. 
BOH ana BS therefore pass into the alcohol layer. 
The hydrolysis equilibrium can be written as 
B + H,O 2 BOH + H: 
hence 
CBOH X Cit = k, CB. 
or also, because 
CBON = CH 
Gro) = Vik, ol: 
To the ordinary electrolytic dissociation of the dye salt applies 
the formula: 
9 
2 
cBz = kh, eB Xe) =f, 
1) Berl. Ber. 52. 1608 (1899). 
