JACQUES LOEB 



839 



If we consider all these complicating circumstances there can be 

 little doubt left that the influence of pH on the viscosity of suspen- 

 sions of particles of gelatin is mainly due to the change in volume of 

 these particles under the influence of the pH and that this change 

 of volume finds its explanation in the Doiman equilibrium between 

 the particles and the surrounding liquid. 



It is well known, and it has been discussed in preceding papers/^ 

 that the viscosity of a gelatin chloride solution, e.g., of pH 3.0, is 



3.5 



o 3.0 



■T-l 



to 



O 

 O 



2.5 



2.0 



1.5 



1.0 



25 



20 



15 «oO 



10 



o 



n .MMMMMNMMM 

 " 2048 1024 512 256 128 64 32 16 8 



Concentration ol'NaNOg 



Fig. 6. Showing depressing influence of neutral salts on viscosity of suspensions 

 of powdered gelatin in water and on the volume occupied by the gelatin particles 

 in the suspension. 



lowered when neutral salts are added and the. pH kept constant. 

 The same is true for the viscosity of suspensions of powdered gelatin. 

 Doses of 0,5 gm. of powdered gelatin of pH 6.0, going through Sieve 

 100 but not through Sieve 120, were put each into 100 cc. of water 

 containing 6 cc. of 0.1 N HCl, and different quantities of NaNOs, so 

 that the concentration of the salt varied in the different solutions from 

 m/8 to m/2048. One solution contained no salt. The pH of the 



^5 Loeb, J., /. Gen. Physiol, 1920-21, iii, 391. 



