Skey. — Osomose, as the Cause of Susjjension of Clay in Water. 489 



There is, perliaps, one point in respect to this, about which you may 

 require further information ere you would be prepared to give an opinion 

 respecting the accuracy of my theory. It may be asked whether, in all 

 instances of persistent clay diffusion, there is sufficient soluble saline matter 

 present of such a nature, and which is, besides, so unevenly distributed, as 

 to enable dialysis to be carried on to the necessary extent ? 



In regard to this, I would reiterate the statement which I have made, 

 that dialysis is best produced by very weak saline solution, and I. would, 

 besides, remind you thfit by far the most effective solutions for this purpose 

 are those of the alkalies, and it is precisely matter of this kind, which, as it 

 happens, is certain to be present and unequally distributed in any clay 

 water we may ever prepare. 



In all clay, as you are aware, some alkaline matter is present, and in 

 such a form that it gradually passes into solution. Again, ammonia 

 can, as we know, scarcely be excluded from the water through which clay 

 may be diffused, and it signifies not where the alkalies are, whether with 

 the clay or the water, so long as they are not equally diffused throughout 

 both. 



In this connection it is proper to note the fact which has been recently 

 discovered* : — " That the power which water possesses of sustaining clay in 

 suspension is increased by the addition of small quantities of the alkalies or 

 their carbonates," and that water, whose power of sustaining clay had been 

 destroyed by_an acid, had this power restored in great measure by any of 

 the alkalies. Now precisely the same kind of thing would happen in the 

 case of albumen, and conversely salts in large quantity retard or prevent 

 the alkalies acting in this manner. The analogy therefore between clay and 

 albumen in respect to my subject, is obviously of so wide and general a 

 character that we may safely assume them to be alike capable of assisting 

 in osomotic action and its results. 



In conclusion, I would state that I have thus singled out the persistent 

 suspension of clay for explanation in place of the persistent suspension of 

 substances of a like nature generally, because the question of clay suspen= 

 sion is to me of particular interest as being one I have had in my mind for 

 a long time past, and I obtained by experiment results thereon which I am 

 persuaded are of some value in regard to its settlement. 



Granted, however, that this attempt of mine at the explanation of the 

 persistent suspension of clay is a successful one, the principle thus involved 

 is so easy to make a general application of, to the explanation of those 



* Suspension of Clay in Water, by William Durham, F.E.S.E. Kead before the 

 Physical Society of Edinburgh, 28th January, 1874* 



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