6o Studies of Diffusion through Rubber Memhranes [Sept. 



pressure of the ether was obviously without mechanical effect. But 

 in a miniite or two downward diffusion currents were visible along 

 the surface of the bag and oil rose rapidly in the tube. 



After the initial effects of the ether had been shown, the bottle 

 was filled with ether containing Sudan III, and a 5-foot vertical 

 extension of the same bore was added to the upright glass tube. 

 In a moment the upward movement of the liquid was markedly 

 accelerated. 



The demonstration was started at about 9 p. m. At 10 p. m. 

 the osmotic pressure had carried the column of oily fluid to the top 

 of the lo-foot tube, and liquid continued to run rapidly from the 

 Upper orifice until the apparatus was dismantled after the adjourn- 

 ment of the meeting, at about 11.30 p. m. 



During the progress of the demonstration, Sudan III diffused 

 rapidly from the exterior, through the rubber, to the very top of the 

 rising column of fluid, before any of the liquid passed out of the 

 Upper opening. Oil diffused rapidly through the rubber into the 

 ether. 



The second demonstration was essentially the same in principle 

 and technic as the first. Instead of a lo-foot upright tube, however, 

 the authors substituted an L tube with an inside diameter of 6 mm. 

 The vertical extension of the tube was 17 inches, the horizontal ex- 

 tension was only 3 inches. The latter extension was drawn out to 

 a narrow bore in an inclined plane, to facilitate direct delivery of 

 any liquid that might pass through that end of the tube. 



When partial immersion of the bag first occurred there was no 

 visible response, but, in a minute or two, oil began to rise in the 

 tube. The bag was then completely covered with ether. The up- 

 ward movement proceeded rapidly ; and in about an hour nearly 200 

 c.c. of liquid passed through the upper orifice into a graduated cylin- 

 der which was supported underneath the outlet to catch the overflow. 



IV. A DEMONSTRATION OF THE DIFFUSION OF PIGMENTS 

 FROM FAT THROUGH RUBBER INTO FAT»" 



The writer has found that many fat-soluble pigments, such as 



Sudan III and Scarlet R, diffuse readily from solid and liquid fats 



" Gies : Proceedings of the Society for Experimental Biology and Mediane, 

 191 1, viii, p. 73. 



