A Few Popular Facts About Diffusion. 37 



itself and the other salts which are capable of assuming 

 a crystalline form : — (b) " Colloids," embracing the 

 gummy or mucilaginous matters which are not capable 

 of crystallization. 



In cane-juice, these two classes of bodies exist in most 

 intimate association in the cells of the cane-plant, and 

 they are distinguished by a remarkable physical fa6l, 

 which forms the basis of all modifications of the diffusion 

 process. This fa6l is the difference which they manifest 

 with regard to the power of passing through moist water- 

 tight membranes. The crystalloids, when dissolved in 

 water, will readily pass through vegetable and animal 

 membranes, when there is water in circulation on the 

 outside; the colloids are not possessed of that property 

 to nearly the same extent ; and thus, as I have already 

 said, by the immersion of the cane-slices in circulating 

 water, as in the diffusion process, we ought to be able 

 to procure a juice much purer than that obtained by the 

 aid of mills ; for the dead cell-walls of the cane-slices 

 form an excellent dialyser, and the sugar should pass on 

 to manufa6lure, while the gummy matters remain within 

 the cells, A greater extraction of sugar from the cane 

 is likewise obtainable through the application of this 

 natural law, than by brute force. 



The pra6lice of the diffusion-process may be des- 

 cribed as follows : — The cane-slices are brought into 

 conta6l with the ordinary estate's trench-waten Then, 

 by theory, if the cells in the cane-slices contain 12 0/0 of 

 sucrose, transfusion will go on till an equal weight of 

 water contains 6 0/0 of sugar, while by the passage of 

 water into the cell, the juice therein is reduced to the 

 same density as that of the exterior solution. Taking 



