488 Transactions. — Chemistry. 



It is therefore quite certain that any substance capable of dialyzing will, 

 when swung clear of all attachments in pure water, describe movements 

 of great persistency which are due to osomose, and in order to complete 

 the evidence which is yet required to show that osomose is the cause of 

 the persistent suspension of clay in water, it only remains to be shown 

 that this substance (clay) is capable of dialyzing. 



For this purpose I adduce Prof. Graham's opinion of the mode in which 

 osomose is effected (an opinion in which I fully concur). This able chemist 

 (the discoverer, by the way, of osomose) attributes it entirely to the exertion 

 of chemical affinity. Any dialyzing diaphragm having water on the one 

 side and saline water on the other, is, he holds, constantly absorbing, that 

 is combining with water towards the side which is in contact with water 

 alone, and giving it up to the other side, that is, to the saline solution there. 



Thus it appears that any substance which, while insoluble, or nearly so, 

 in water, can still weakly combine with it, and in various proportions, is 

 competent to dialyze. 



Now, clay is most certainly such a substance ; it hydrates readily, and 

 is as readily de-hydratad, that is in part, and the proportion in which it 

 hydrates manifestly varies, and under the very conditions it is necessary 

 that it should do so for my argument, that is, as placed in pure water and 

 saline water, as is manifest to the eye even when clay in water is coagulated 

 by salt. 



Indeed, Prof. Grraham has shown that porous earthenware dialyzes ; he, 

 however, attributed this property to the alumina present therein ; but I fail 

 to see how alumina could be liberated from the earthenware in his experi- 

 ment. I should rather attribute the effect he observed to that portion of 

 the ware which had been hydrated to clay. 



It is therefore, I think, now clearly shown that clay is capable of 

 dialyzing, and so is competent, under conditions already named, to describe 

 movements due to osomose. 



The principal cause, then, if not indeed the sole cause, of the persistent 

 suspension of clay in water, is undoubtedly motion communicated to it by 

 osomose ; and as osomose is the more rapidly produced in saline solutions 

 the weaker they are, and further, as the motion thereby derivable should be 

 applied with greater effect to clay particles the more hydrated and, con- 

 sequently, the lighter they are, it follows that suspension of clay in water 

 will be the more persistent the less saline the water is — a fact which, as 

 you may remember, I have long since demonstrated. 



In water saline to a certain extent, clay particles by de-hydration acquire 

 a density too great to allow of their remaining sensitive to the motion proper 

 to osomose ; they therefore coalesce, and gravity soon asserts itself* 



