220 



THEORY OF COLLOIDAL BEHAVIOR 



kept standing for a day at a temperature of, e.g., 10C., is due to 

 the formation of particles of solid jelly, then if this solution is 

 heated to 45C. and cooled rapidly to 20C. the majority of these 

 solid particles should have melted and dissolved into isolated 



I 



2.7 

 2.6 

 2.5 

 2.4 

 2.3 



zz 



o 1>9 



> I 1 ? 



.1.6 



1.5 

 1.4 

 1.3 

 1.2 

 1.1 



i i r 



i i i 



Influence of NaCl on 

 the rise in viscosity of 

 17o gelatin chloride 

 solution of pH 3.4 on 

 standing at 20 C 



5 



10 15 20 25 30 35 40 45 50 55 60 



Time in minutes 



FIG. 61. Showing that NaCl solutions up to a concentration of 1M have no 

 effect on the increase in viscosity of gelatin chloride solution of pH 3.4 on stand- 

 ing at 20C. 



ions or molecules. Hence such a solution when cooled rapidly 

 to 20 should show at this temperature a considerably lower 

 viscosity than the same solution shows at 20 when it is brought 

 to this temperature directly from 10C. without previous heating 

 to 45C. The experiment represented in Fig. 62 shows that this is 

 the case. 



