THE NEW THEORY OF SOLUTIONS. 



DIQSMOSE. 



MANY of the investigations of the older physiolo- 

 gists were concerned with the passage of liquids 

 through animal membranes. If an aqueous solution were 

 introduced into a vessel, the base of which consisted 

 of a piece of bladder, on immersing the vessel in water 

 until the levels of liquid within and without were the 

 same, numerous observations established the fact that 

 both water and dissolved substance began to traverse the 

 membrane. In the same apparatus the rates at which 

 these movements took place varied with the concentra- 

 tion of the solution and the nature of the dissolved sub- 

 stance, but it invariably happened that water passed 

 through the membrane more rapidly than the saline 

 substances present in the solution. For this reason the 

 volume of the solution began to increase. Pressure thus 

 began to rise on the solution-side of the membrane, and 

 continued to augment until it reached a limiting value. 

 Such phenomena received the name of endosmose, the 

 term exosmose being applied to what occurs when water 

 is placed within and solution without the vessel, and the 

 apparatus employed was termed by Dutrochet an endos- 

 mometer. 



The most noteworthy attempt to obtain quantitative 

 measurements of what was taking place in these experi- 

 ments was made by Jolly. In his method the endosmo- 

 meter is kept immersed in water which is constantly 

 renewed, consequently endosmose only reaches its limit at 

 the instant when all the dissolved substance has escaped 

 and the apparatus contains only pure water. When this 

 state of things is attained, the ratio of the weight of 

 water which has passed into the vessel to the weight of 

 dissolved substance which has escaped Jolly termed the 

 endosmotic equivalent of the substance with reference 



