483 
over, the formation of the insoluble precipitate in the fibre could only 
start when a certain concentration had been attained in the bath. 
Neither of these phenomena have, however, been observed. The 
absorption of the dyestuff increases regularly with its concentration in 
the bath and there is no question of a discontinuity in this absorption. 
The chemical theory is, therefore, an improbable one and is, in 
fact, rejected by the majority of the investigators of dye absorptions. 
The theory of the solid solution has been proposed first by O. 
N. Wirt?) and was at first universally accepted. Wirt, by a number 
of examples has rendered it indeed plausible that the condition in 
which the colouring matter is present in the fibre is perfectly com- 
parable with that of a substance in solution, that there is an equi- 
librium between the dyestuff in the fibre and in the aqueous solution 
and that the changes in that equilibrium, caused by the addition of 
another solvent such as alcohol, or of acids or salts, agree qualita- 
tively, exactly with those in the equilibrium between two non-miscible 
liquids in which a third substance is dissolved. 
In the quantitative investigation as to the distribution of the 
dyestuff between the fibre and the bath, it has been found, 
however, that tliis distribution does not take place according to 
v 
age l 
Henry’s law, but that the adsorption-formula ——=ae /" must be 
m 
applied. 
Mainly on account of this, WALKER and APPLEYARD’) as well as 
Scumipt*), FREUNDLICH and Losrv *), Groreinvics °), PrLet-Joniver °) 
and others conclude that Wirr’s theory cannot be correct and that 
the colouration is, in the first instance, an adsorption phenomenon ‘), 
Hence, a very high value is attached to this utterly empirical and 
very elastic formula, which in FreunpLicn and Losry’s determinations 
1) Färberzeitung 1890/91, 1. 
2) Journ. Chem. Soc. 69, 1334 (1896). 
3) Zeitschr. f. physik. Chem. 15, 56 (1894). 
4) Le, and Freunpuicu, Koll. Zeitschr. 3, 212 1908), 
be be: 
6) L. Perer-Joriver, Die Theorie des Färbeprozesses, 1910. 
7) According to Freunpricu and Losev the fixation of the dye after its absorption. 
takes place because the colouring matter was either dissolved in a colloidal state 
and then rendered insoluble by coagulation by the fibre (in the case of substantive 
dyes), or was dissolved molecularly but converted in the fibre into an insoluble 
or colloidal non-diffusing substance. As regards this last change the action of 
another adsorbed substance (the mordant) or of the fibrous matter would, however, 
have to be considered eventually. 
Perer-Jorver also regards the fixation of the dye chiefly as a coagulation of 
colloids. 
32* 
