62 Studies of Diffusion through Rubber Membranes [Sept. 



immersed in olive oil, and the remaining conditions of the environ- 

 ment are uniform, diffusion of the pigment promptly occurs through 

 rubber, but does not take place at all through any of the other three 

 membranes. When the bags are lifted from the oil, washed ex- 

 ternally with ether, and then immersed in ether,^^ the pigment 

 quickly passes through the rubber, but diffuses very slowly if at all 

 through the remaining membranes. 



Successive immersions of nioist impermeable membranes (gold- 

 beater's skin and parchment) in alcohol and ether, for different 

 periods of time, fail to render the treated membranes more perme- 

 able to Sudan III than before. 



The authors demonstrated the general facts in this connection 

 pertaining to rubber and gold-beater's skin. 



VI. EXPERIMENTS ON THE DIFFUSIBILITY OF ALKALOIDS 



THROUGH RUBBER^" 



Various ether-soluble substances, when dissolved in ether and 

 placed in rubber bags immersed in ether, readily pass through the 

 rubber membranes thus imposed (I-V). We have found that 

 various alkaloids and some related substances readily diffuse 

 through rubber under such conditions. 



Our experiments were conducted as follows : A moderate quan- 

 tity of the pure ether-soluble substance was mixed with 15 to 25 c.c. 

 of ether.^^ This mixture was poured through a funnel into a new 

 air-tight rubber condom in such a way as to preclude the possibility 

 of overflow upon the external surface. The bag was then immersed 

 in about 50 c.c. of ether in a narrow salt-mouth bottle 7 inches high. 

 With the bag suspended at füll extension in this position, its mouth 

 was about an inch above the opening in the bottle. The protrud- 



"In experiments which the senior author has been conducting with Prof. 

 Welker's Cooperation, it has been found that collodion bags are disintegrated by 

 ether containing more than about 1.5 per cent. of alcohol. Pure ether does not 

 dissolve or in any way disorganize collodion membranes. A collodion bag con- 

 taining pure ether may be immersed for a week or more in pure ether without 

 undergoing any appreciable deterioration. (See page 70.) 



^ Sidbury and Gies : Proceedings of the Society for Experimental Biology 

 and Medicine, 191 1, viii, p. 104. 



" Substances which did not dissolve readily were triturated with ether in a 

 mortar. 



