Ball — On the Action of Pedase. 351 



1 c.e. of distilled water was added to 1 c.c. of 2 per cent, pectin solution 

 in a test-tube, and 1 c.o. of freshly extracted sap from the leaves of Syringa 

 was put into a similar tube. The two tubes were partly immersed in a large 

 glass tank of water for about ten minutes, in order that their contents might 

 come to the same temperature. At a noted time the contents of the tubes 

 were mixed, and the mixture poured into a Hamburger conductivity tube, 

 which was also immersed iu the same tank of water at 13° 0. Measurements 

 of the resistance of the mixture were made every ten minutes by comparison 

 with a standard resistance, using a metre bridge with an alternating 

 current and telephone. 



The resistance of the mixture remained practically constant for over two 

 hours, and at the end of this time a solid jelly had been formed in the 

 conductivity tube. During the experiment the temperature of the water in 

 the tank was constant within 0"5° C. 



The product of the action of pectase therefore consists of a spongy net- 

 work composed of a more or less solid phase, in the meshes of which a more 

 liquid phase is distributed. 



Measurement of the c/iange in viscosity. — In order to measure the change in 

 viscosity, a viscosimeter of the Ostwald type was constructed. This consisted 

 of a (J-tube made of glass tubing. Part of one limb was composed of a piece 

 of thermometer tubing, and above this capillary the tube was dilated into a 

 small bulb. 3 c.c. was the amount of liquid which was always used, and this 

 was introduced by means of a pipette. In use the liquid was sucked up to 

 a definite height above the bulb in the limb of the (J-tube which contained 

 the capillary, and was then allowed to run back. The time taken by the 

 meniscus in passing between marks on two constrictions above and below the 

 bulb was determined by means of a stop-watch. As this piece of apparatus 

 was not sufficiently accurate to permit absolute determinations of the viscosity 

 being made, the times taken for the meniscus to pass between the two marks 

 were compared with one another. 



In the experiments at a temperature above 0° C. the viscosimeter was 

 partly immersed in a tank of water containing about twenty litres. This was 

 kept at a constant temperature by the introduction of either hot or cold 

 water from a tap connected with another tank. The water in the tank was 

 kept well stirred, and a sensive thermometer attached to the viscosimeter was 

 easily maintained wittiin 0'1° 0. of any desired temperature. 



The viscosimeter was standardized with 3 c.cs. of distilled water at 0"^ C, 

 and the time for emptying the bulb was 3*0 seconds. 



3 L 2 



