DEPARTMENT OF BOTANICAL RESEARCH. 75 



given above absorbed water faster and took up a larger total of water 

 than did the jelly made from water alone. Parallel tests to determine 

 the rate at which gelatine jelly made with water alone absorbs these 

 same solutions showed the usual results, namely, in the cases of sodium 

 chloride, ammonium chloride, and sodium bromide the rate is faster 

 than it is for water, and in the other cases slower than it is for water. 

 This work has shown, then, that it is not safe to draw conclusions 

 regarding the effect which substances wdthin a jelly exert upon its 

 imbibitional capacity, when evidence for such a conclusion lies in the 

 known effect of an external solution of the same substance on that 

 jelly. This applies to the theories involving the physico-chemical 

 effect of the substances upon the gelatine itself as well as those con- 

 cerning physiological phenomena. 



EFFECT OF HEAT ON IMBIBITION OF WATER BY GELATINE. 



Some confusion exists in the hterature regarding the effect of heat 

 on the absorption of water by gelatine. It is claimed, for example, 

 by Taylor that (according to le ChateUer's theorem) heat mil hinder 

 or diminish imbibition, while cold will increase it. The matter has 

 been investigated in a series of tests made at 10°, 20°, and 32° C. 

 The rates of absorption and the maximum water-content were obtained 

 for 500 pieces of gelatine of various sizes, the gelatine being in various 

 initial conditions of water-content. Invariably the higher the tem- 

 perature the greater was the rate of imbibition and the larger the 

 maximum water-content at the point of apparent equilibrium. 



This theorem of le Chatelier is applicable only to equilibrium 

 phenomena, and it is probable that gelatine and water do not reach 

 a true equilibrium at ordinary^ temperatures. In a large number of 

 attempts to find a true equilibrium no absolute maximum of water- 

 content was found. As the maximum is approached, a very appre- 

 ciable amount of gelatine passes from the surfaces of the pieces and 

 becomes dispersed in the water. "WTienever an apparent maximum 

 was reached it could be increased by separating the pieces of gelatine 

 into smaller fragments. Bacterial action prevented continuing any 

 given experiment longer than 4 weeks at temperatures from 10° to 20° 

 C. or 2 weeks at temperatures above 25° C. Consequently it was not 

 possible to show that a piece of gelatine will become completely 

 dispersed in water at the temperatures used. But the e\'idence all 

 goes to show that at these temperatures gelatine takes up water to at 

 least nearly unlimited amounts when given unlimited time. Certainly, 

 there is no temperature between 10° and 30° C. where a true point of 

 equilibrium is reached within less than 2 weeks. Since the rates of 

 absorption closely approach a hyperbolic curve when plotted, it may 

 be assumed that the equilibrium-point is never reached. It thus 

 seems highly probable that le ChateUer's theorem is not applicable 

 to the phenomena of imbibition of water by gelatine. 



