JACQUES LOEB 



103 



is strikingly illustrated by Fig. 4. Gelatin chloride solutions all 

 containing 1 gm. of originally isoelectric gelatin were brought to 

 various pH by adding HCl and were at the beginning of the experiment 

 all heated rapidly to 45° and cooled at once to 20°C. Then the viscos- 

 ity was measured immediately at 20°. The result is given in the lowest 

 curve in Fig. 4. The solutions were kept at 20° for 1 hour and the 

 viscosity measurements were repeated. The middle curve in Fig. 4 



2.6 

 2.5 

 2.4 

 2.3 

 2.2 

 2.1 

 20 



<3 



o 



§ 1-8 



> 1.7 



1.6 



1.5 



1.4 



1.3 



1.2 



pHi 



.4 1.6 1.8 20 2.2 24 2.6 26 3.0 3.2 34 3.6 3.8 40 42 44 4.6 

 Fig. 4. See legend of Fig. 3. 



shows that at this time the viscosity of the isoelectric solution had 

 increased considerably, that of the solutions of lower pH down to 

 3.0 had increased the less, the lower the pH. Below pH 3.0 no in- 

 crease in the viscosity had occurred. 2 hours later another viscosity 

 measurement was made; the results are represented in the upper curve 

 of Fig. 4. At the isoelectric point the viscosity had increased enor- 

 mously, but less and less at lower pH. During all the time and also 



