Chemistry. — ''Contributions to the theoi^i/ of dyeinq" (First commu- 

 nication) by Prof. H. R. Kruyt and Miss J. E. M. van der Made. 

 (Commiinicated by Prof. Ernst Cohen). 



(Communicated in the meeting of June 3", 1917). 



1. Three different explanations have been suggested for the way 

 in wliicli dyes are taken up by fibres and other solids. First a 

 merely chemical combination of dye and fibre was suggested ; but 

 a chemical theory gave rise to so many contradictions, ttiat, as soon 

 as the theory of solid solutions was developed, it was tried to explain 

 dyeing in agreement with the new theory. But in this way it was 

 just as impossible to bring experiments and theory into harmony, 

 and the new knowledge in the chemistry of colloids, especially that 

 of the phenomena of adsorption and of the electricity of contact, 

 gave a better starting-point for the explanation of the way in which 

 wool, silk, cotton etc. take dyes from their solutions in water^ 

 both when electrolj tes are added and when this is not the case. 

 Freundlich, in collaboration with several pupils (Losev ^), NeUiMann *)), 

 stated the fact, that amorph. carbon takes ihe dye from its solution 

 in quite the same way as textile-fibres do; Pelet ') has made 

 numerous investigations with his pupils on this siibject ■*). It may 

 be stated that nowadays the interpretation of the process of dyeing 

 as a phenomenon of electro-adsorption is generally accepted. 



This point of view may be summarized as follows: the facult}- 

 of the fibre to take up the dye depends on the electric potential 

 at the confines of fibre and solution, in connection with the sign 

 of the electric charge of the dye-ions. The fibres and charcoal are 

 charged negatively with regard to water, therefore the}' generally 

 adsorb the basic dyes better than acid dyes. Every influence increasing 

 the negative charge of the adsorbentia, will increase the adsorption 



1) Zeitschr. f. physik. Ghem. 59, 284 (1907). 



2) Zeitschr. f. physik. Ghem. 67, 538 (1909;. 



^) The results of these investigations are brought together in the interesting 

 monograph Pelet-Jolivet, Die Theorie des Farbeprozesses (Dresden 1910). 



^) Bancroft and his pupils too have paid much attention to the process of 

 dyeing of late years.. A summary of the theory of dyeing can be found: W. D. 

 Bancroft, Journ. of physical chemistry 18, 1, 118 and 385 (1914). 



