641 



considered till now \\ For without sufficient reason it is only electro- 

 adsorbative-phenoniena that have been compared with the process 

 of dyeing; the investigation of Freundlich and Poskr '^) showed 

 however that such a way of interpretation is quite insufficient. 

 Adsorption is not determined by electrical causes only, besides 

 there is certainly a non electrical adsorption, determined by the surface 

 tension according to Gibbs' law. As tlie lyotropic series shows the 

 sequence in whicii the ions influence surface tension, it will be 

 clear that the principle of adsorption explains both tiie importance 

 of valency and lyotropic strength. 



Attention must all the same be directed to the possibility, that 

 the electrolytes do not leave the dyesolutions itself') unaltered. The 

 peculiar condition of dyesolutions, often polydispers with the character 

 of a pseudo-binary system ■*), make the problem all the more com- 

 plicated ; only a wide investigation of each sort of influence by 

 itself can make it clear. Hence we already made a beginning 

 with such experiments. 



Utrecht, June 1917. van 't Royy -lab oratory. 



^) The only investigation showing the lyotropic influence on dyeing is to be 

 found Biochemical Journal 1 175 (1906). Bayuss made some researches on the 

 dyeing of filtering paper by congo-red in presence of salt; the influence of these 

 salts proved to be as according to the lyotropic series. Bancroft (loc. cit.) does 

 not mention this paper, Pelet-Jolivet does, but only in connection with other 

 questions. So Bayliss' paper came to our knowledge only when this investigation 

 was closed. 



3) Koll. Beih. 6, 297 (1914). 



3) See I. Teaube, Koll. Beih. 3, 237 (1912). 



^) The remarkable observation Droogleever Fortuyn published [These Proceed- 

 ings 23 1380 (1915)] have convinced us again on this point. It is obvious that 

 in a solution of new fuchsine in water there are two kinds of molecules, a coloured 

 and a non coloured one, which are in equilibrium with one another. And in water 

 this equilibrium is reached only after a long time and as by absorption only the 

 coloured modification is taken away, some days are wanted to colour the water 

 again after it has been decoloured by coal (acetic acid seems to catalyse). It is a 

 wellknown phenomenon that a solution of fuchsine is decoloured by alcali as the 

 dye is changed into the pseudo base; still such a solution will dye silk [Jacquemin, 

 G.R. 82, 261, (1876)] and wool. But the red colour returns too when the solution 

 is shaken with isoamylic- or isobutylic alcohol [Witt, Farber Zeitung 1, 1 (1891)]. 

 The same thing occurs when we shake a solution decoloured in the same way 

 as followed by Droogleever Fortuyn, with isobutylic alcohol ; this suggests that 

 water is a solution of a pseudo base, which was present already in the primary 

 solution. Perhaps this is also the reason, why the adsorption of dyes seems to 

 take much more time than that of other bodies. The regeneration of dye, the 

 only component which has really been adsorbed, from the carbinol base, which 

 is even not in real solution (as an ultramicroscopic investigation shows), makes 

 it appear as if the process of adsorption should be slow in this case. 



