419 



particles are chiefly to be considered. It may be derived from the 

 formula that when the size of the particles increases n' times (and 

 as the concentration remains equal the distance increases ?i X) the 

 intensity becomes n' X greater. I _ belie\'e that there is, therefore, 

 every reason to assume that a modification in the size of the gelatin- 

 particles is responsible for the investigated phenomenon.') 



A number of other variations in the gelatin solutions always take 

 place perfectly continuously, nor is a sudden change of intensity 

 ever observed in the Tyndalj. phenomenon at a definite temperature. 

 So there cannot exist a temperature at which the size of the gelatin 

 particles suddenly changes; it must much sooner be assumed that 

 large and small particles always occur side by side, and when in 

 a solution a change of the intensity takes place, this points to a 

 modification in the mutual relation. It is probable that there exists 

 a great number of possible combinations; for simplicity's sake it 

 will be assumed in what follows that the gelatin only occurs in 

 two forms, large (L) and small (S) particles, so that we may say 



L 



= f{T\. 



I have supplemented my earlier determinations by ascertaining 

 the relation between the temperature and the equilibrium intensity 

 at that temperature for several concentrations. Again a solution 

 containing glycerin was used for this. I did not consider every state 

 which remained constant at a certain tempei-ature, as a true equi- 

 librium. This was only done when it appeared to be the limit which 

 was reached in course of time, both when the initial intensity was 

 greater and when it was smaller. The results are given in fig. 1. 

 For each of the examined concentrations the intensity at 70^ has 

 been assumed as unity; so it is only possible to draw conclusions with 

 regard to the way in which the equilibrium intensity varies with 

 the temperature: the figure is not adapted for a comparison of the 

 absolute values for the different concentrations. For so far as the 

 character of the equilibrium line is established, the line is drawn; 

 when this is not the case, it is dotted; the dotted part is left out 

 of consideration here. 



If the variation of the intensity only depended on the temperature, 

 the curves for the different concentrations would have to coincide. 

 This is, however, by no means the case: for the V4 7o solution the 

 line ascends only slowly from right to left throughout the inves- 



1) See also von Menz. Zs. f. Pliysik. Ghem. 66. 129. 1908. Bachmann Zs 

 Anorp;. Gliem. 73. 1911. 



27* 



