CAUSES OF THE MOTION OF JUICES. 391 



If the water be colored by indigo or cherry juice, its 

 motion may be followed- by the eye, and after a certain 

 lapse of time the water and alcohol will be seen to have 

 become uniformly mixed throughout the two vessels. 

 This manifestation of adhesive attraction is termed Liq- 

 uid Diffusion. 



What is true of two liquids likewise holds for two 

 solutions, i. e., for two solids made liquid by the action 

 of a solvent. A vial filled with colored brine, or syrup, 

 and placed in a vessel of water, will discharge its con- 

 tents into the latter, itself receiving water in return ; 

 and this motion of the liquids will not cease until the 

 whole is uniform in composition, i. e., until every mole- 

 cule of salt or sugar is equally attracted by all the mole- 

 cules of water. 



When several or a large number of soluble substances 

 are placed together in water, the diffusion of each one 

 throughout the entire liquid will go on in the same way 

 until the mixture is homogeneous. 



Liquid Diffusion may be a Cause of Continual 

 Movement whenever circumstances produce continual 

 disturbances in the composition of a solution or in that 

 of a mixture of liquids. 



If into a mixture of two liquids we introduce a solid 

 body which is able to combine chemically with, and 

 solidify one of the liquids, the molecules of this liquid 

 will begin to move toward the solid body from all points, 

 and this motion will cease only when the solid is able to 

 combine with no more of the one liquid, or no more 

 remains for it to unite with. Thus, when quicklime is 

 placed in a mixture of alcohol and water, the water is in 

 time completely condensed in the lime, and the alcohol 

 is rendered anhydrous. 



Rate of Diffusion — The rate of diffusion varies with 

 the nature of the liquids ; if solutions, with their degree 

 of concentration and with the temperature. 



