THE PECTIC SUBSTANCES 71 



to the maximum value of the viscosity becoming smaller. 

 There is, however, an alternative explanation possible, that 

 the low value is due to a decrease in the activity of the 

 enzyme during its storage for one day. The form of the 

 curve, however, is against this view, for it shows that the 

 initial velocity is not very much less than in No. III. 



In order to obtain decisive evidence, the enzymes of 

 3 c.c. of freshly pressed sap were precipitated by the ad- 

 dition of 15 c.c. of 95 per cent, spirit. After centrifuging, 

 the precipitate, which was almost free from electrolytes, was 

 redissolved in 3 c.c. distilled water, and, as in other experi- 

 ments, 1 c.c. was added to the pectin solution. The curve 

 No. VII., obtained in this way, shows the rapidity of the 

 coagulation to be great. The viscosity was such that 

 about 500 seconds was required for the emptying of the 

 bulb, whereas at the start, less than four hours previously 

 3' 8 seconds sufficed. After four hours no flow took place 

 This furnishes direct and conclusive evidence that re- 

 moval of electrolytes, including of course the calcium salts, 

 results in the increase of the viscosity of the solution of 

 transformed pectin up to a point far in excess of that 

 attained to by any similar solution containing electrolytes. 

 Traces of electrolytes were, however, still present, having 

 been adsorbed by the precipitated enzymes. In view of 

 the minute traces of calcium salts ordinarily found in plant 

 juices, the amount remaining must have been negligibly 

 small. Direct experiments are being undertaken to test 

 this point.* 



On the whole, it seems to be well established by Ball's 

 results that the two effects, the production of a gel by the 

 action of pectase and the clumping of the material of the 

 gel by electrolytes, are distinct, and were probably c onf used 



* This work has had to be postponed, for Mr. Ball has received a 

 commission in the army for the duration of the war against Germany. 



