VISCOSITY 



219 



longer increases on standing when the concentration of CaCU is 

 M/2 or 1 M. In this concentration CaCl2 causes a slight increase 

 in the rate of solution of gelatin chloride. 



NaCl causes no change in the rate of solution of gelatin chloride 

 as long as the concentration of NaCl does not exceed 1 M. 

 Above this concentration it causes coagulation and the viscosity 



Influence of CaCl 2 on 

 the rise in viscosity of 

 1% gelatin chloride 

 solution of pH 3.4 on 

 standing at 20 C. 



2.7 



2.6 



2.5 



2.4 



2.3 



S 2.2 

 ^ 2.1 

 8 2.0 



.2 L9 



^ 1.8 

 1.7 

 1.6 

 1.5 



1.4 



5 10 15 20 25 30 35 40 45 50 55 60 



Time in minutes 



FIG. 60. Showing that concentrations of CaCh or M/2 or above prevent 

 the increase in viscosity of gelatin chloride solution of pH 3.4 on standing 

 at 20C. 



can no longer be measured. Hence NaCl in concentrations up 

 to 1 M should not alter the rate of increase of viscosity of gelatin 

 chloride solutions on standing. Figure 61 shows that this is 

 correct. 



The simplest method of melting solid particles of jelly is by 

 heating to 45C. If, therefore, the striking increase in viscosity 

 which occurs when a 0.5 per cent solution of isoelectric gelatin is 



