Ball — On the Action of Pectase. 355 



Sap was extracted from the leaves in tlie usual manner, and centrifuged. 

 To 3 CCS. of the sap 15 ccs. of spirit was added, and the liquid containing the 

 precipitated protoplasm and enzymes was centrifuged and the clear liquid 

 poured off. The residue was dissolved in 3 ccs. of distilled water, and 1 cc. of 

 the solution was used instead of the ordinary sap, but otherwise details of the 

 experiment were the same as in the last three. 



The viscosity increased slowly at Urst, and then rapidly. The highest 

 time of flow in the viscosimeter shown on the curve belonging to the experi- 

 ment is only 100 seconds, whereas readings were taken up to nearly 

 500 seconds, and after this the mixture refused to flow through the capillary. 



This experiment shows clearly that removal" of electrolytes removes also 

 the factor which causes clumping of the gel. 



The gel was left in the viscosimeter until next day, when it was found 

 that clumping had taken place in the meantime, probably owing to a trace of 

 electrolytes which had not been removed. 



Discussion of Results. 



These experiments show that the product of action of pectase on pectin 

 has the structure of a gel composed of a semi-solid reticulum, in the meshes 

 of which a liquid is distributed, and also that the gel, when formed, is broken 

 up in the presence of electrolytes by the clumping of the more solid portion 

 into separate aggregates. 



It appears that what has hitherto been described as the coagulation of 

 pectin is made up of two processes, gelification, and subsequent coagulation 

 of the gel. 



Bertrand and Mallevre (2) came to the conclusion that the coagulum 

 formed by the action of pectase is composed of calcium pectate, and not of 

 pectic acid, as previously stated by Fremy (9). They base this conclusion on 

 the fact that tlie coagulum is completely insoluble in feeble alkaline liquids, but 

 dissolves almost instantaneously after having been macerated in dilute 

 hydrochloiic acid, and the resulting solution is found to contain calcium. 

 They also state that if juice, extracted from carrots, which has been 

 decalcified by addition of oxalic acid, be added to a solution of pectin from 

 which calcium has been carefully removed, the mixture remains indefinitely 

 liquid, but the least addition of a soluble calcium salt causes rapid coagulation. 

 They point out that, owing to the very high molecular weight of the pectic 

 compounds, and to the enormous volume which tliey occupy in the gelatinous 

 state, the amount of calcium required for the formation of a coagulum 

 consisting of calcium pectate would be very small. 



