SS6 



illustrating a growing iiitensit} oC the TYNDALL-plienomenoii ; the ralo 

 of the growth, however, was gradually reduced. 



VI, gelatin-solution cooled to J6°— 18' after heating to 70'. 



Readings after: d. 1 d. 2 d. 4 d. 6 d. 7 d. 9 d. 11 d. 



consistence : fl. 



Intensity: 1 2 2 2,5 4 4 5,6 5,6 



We are in a position to record also another experiment carried 

 out at 20° witii a 2"/„ solution and started a few hours after tiie 

 solidificatioji of the solution. For four days the changes were noted. 

 Here also an alteration took place, which was most marked in the first 

 12 hours and then became less conspicuous. 



2"/, gelatin-solution cooled to 20° after heating to 70°. 



Readings after: d. 1/2 d. Id. 1^ d. 2 d. 3 d. 



consistence : solid 



Intensity: 1,4 4 5,6 5,6 5,6 (4)^) 



The last two experiments yielded two series of plates that were 

 very much alike inter se. It is im})0ssible to determine whether 

 they had been taken from a sol or from a gel. The Tyndall-couc does 

 not enable us to tell the one from the other any more than the 

 naked eye does. 



The changes in the 1% and the 27o solutions are not so conspic- 

 uous at high temperatures as at the temperature of the above 

 experiments. At 40° no change could be made out, and if we com- 

 pare the intensities at 40° and at 70°, the difference seems to be 

 nihil. We take it therefore, that beyond 30' the temperature has 

 only little, if any, influence on the intensity and that the increase 

 commences only below 30''. 



Additional experiments were made with 57o ^md lO"/,, solutions. 

 As for the latter we can but say, that changes presumably did 

 occur at various temperatures, but that they could not be clearly 

 demonstrated by our method of working '^). 



The 57o solutions yield results similar to those of the 1 7o ^^^^ 

 the 27o solutions. Here also different values of the intensity of 

 the light correspond to the various temperatures ; changes only appear 

 at lower temperatures. Contrary to the 17o solution, an obvious 

 difference is to be noted in the 57o sol. between the intensity at 

 40° and 70°, as shown in the following table: 



1) In this exposure the comparison surface was not equal to that of the other 

 plates of the series. 



2) The rapid reduction ol the intensity of the diffused light as the pencil pene- 

 trates farther into the solution, renders it difficult to determine the differences in 

 the absolute intensity. 



