46 THE MIXTURE IS INFLUENCED BY THE 



in others only pure water moves, the phenomenon 

 ought not to occur when all the pores are filled with 

 water or with brine, or when the tube is tied with a 

 double, treble, or fourfold bladder. But the pro- 

 perties of bladder are seen in the finest as well as 

 thickest membranes, and one, two, or three layers 

 make no difference in the ultimate result.* 



* With respect to the theory, that, when a saline solution 

 is mixed with pure water, if the two liquids are separated by 

 a membrane, particles of salt alone pass through the pores of the 

 bladder to the water, and particles of water alone to the brine, 

 the following experiments may throw some light on the question. 

 For the sake of greater accuracy, the results were determined by 

 weighing. The apparatus Fig. 3 was used. The tube contained 

 8*67 grammes of saturated brine, in which were 2*284 grammes 

 of salt and 6'38 of water. After 24 hours it had gained 1*79 

 grammes in weight, and it now contained only 0*941 grammes of 

 salt. It had therefore lost 1*343 grammes of salt, and gained 

 3' 13 of water. According to the above theory, 1 atom of salt 

 and 15 atoms of water must have moved past each other; but 

 this is impossible, since 1 atom of salt requires 18 atoms of water 

 for solution, (10 parts of salt to 27 of water). The weight of 

 the pure water in the outer vessel was 19*26 grammes ; con- 

 sequently, the weight of the brine was to that of the pure water as 

 1 : 2-22. In another experiment, in which the weight of the brine 

 in the tube was to that of the water outside, as 1 : 7*98 ; the tube 

 gained 0-822 grammes in weight ; the liquid in the tube contained 

 at first 0*947 grammes of salt ; and 24 hours after, 0*148 grammes : 

 hence, 1*621 grammes of water had entered, while 0*799 grammes 

 of salt had passed out. For 1 atom of salt, which passed from 

 the tube with brine to the vessel with water, there passed from 

 the latter to the former rather more than 13 atoms of water; 

 (for 58*6 parts, or 1 atom of salt, 118 parts of water). 



