Skey. — Osomose, as the Cause of Suspension of Clay in Water. 487 



also, but to a less extent than water, that is, for equal times of contact 

 therewith. 



"When, therefore, a colloid, say of albumen, is formed into a stiff dia- 

 phragm, with water on the one side and an aqueous solution of a crystaUoid 

 upon the other side, having about the same height as that of the water, the 

 level of the liquids is altered by their unequal diffusion through the dia- 

 phragm, that of the water is gradually lowered, while that of the saline 

 solution is raised, until after the lapse of a day or two a very marked 

 change of level is observable. 



These effects are far greater in the case of weak saline solutions than 

 strong ones, and for alkahes and acids than for salts. It is the mechanical, 

 the lifting effect observable in the apparatus described, that I have noted 

 for the elucidation of the phenomenon of clay suspension. 



I make the apphcation as follows : — Exchange the fixed diaphragm of 

 albumen for a highly elastic one of the same material, and for the change of 

 level before observed in the two liquids there is a change in the position of 

 the diaphragm. The albumen will move in a mass transversely away from 

 the saline solution. 



Hence we may be certain that were a fragment of this diaphragm, 

 especially a minute one, placed in a liquid containing some salt unevenly 

 distributed, such fragment would also move, and move in the same du'ec- 

 tion as the diaphragm itself should. 



Again, we may be equally certain that we should obtain similar move- 

 ments by charging the albuminous fragment with a salt unequally, and placing 

 it in water, pure or nearly so. Lastly, movements of a similar nature, 

 but not so rapid, would ensue, were these fragments charged with the salt 

 equally throughout, as some part of their exterior could scarcely fail to be 

 of more angular construction or to be more porous than the remaining 

 parts, and so would take up water at a greater speed than the other parts, 

 thereby causing a recession of the fragments from the liquid at such points 

 of contact, precisely in the same way that I have shown the movements of 

 camphor upon water are produced."^' 



Thus by progressive changes in the common form of dialytic apparatus, 

 we have at last an apparatus of this kind consisting of a vessel of pure 

 water in which are minute homogeneous fragments of albumen, evenly 

 charged with a salt, one by which all the motion produced by dialysis thereby 

 is communicated to the dialyzing material itself, that is to the minute 

 albuminous fragments. The same result would of course follow were the 

 albumen pure and the water saHne. 



* Vide supra, Art. LXXXI. 



