80 Intelligence and Miscellaneous Articles, 



PHENOMENA OF TRANSPORT THROUGH POROUS BODIES : APPLI- 

 CATION TO DIRECT ANALYSIS : DIALYSIS. BY M. ERN. GUINET. 



After a very brief analysis of Mr. Graham's researches, the author 

 proceeds as follows : — 



Having experienced certain difficulties in the use of vegetable 

 parchment, I endeavoured to replace the dialyser by a porous vessel 

 of pipeclay, such as are used for batteries, instead of which it 

 would be better to use shallow vessels. I have repeated most of 

 Mr. Graham's principal experiments, and have made some which 

 appeared impossible with vegetable parchment. 



The following are some of them : — 



Solution of gum and sugar, in which is immersed a porous vessel 

 containing pure water. At the expiration of twenty-four hours a 

 great part of the sugar has traversed the porous vessel, and is dis- 

 solved in the water, which does not contain a trace of gum. 



Solution of caramel and of bichromate of potass. The salt traverses 

 the porous vessel alone ; the separation is speedily effected. If a 

 drop of the mixed solutions is allowed to fall on a porous vessel, a 

 brown spot of caramel is obtained, surrounded by a yellow one of 

 bichromate, which shows the more rapid diffusion of the latter 

 salt. 



Cotton dissolved in ammoniacal solution of copper. The water in 

 the porous vessel becomes blue from dissolving ammoniacal oxide of 

 copper ; the cotton remains on the outside. The evident object of 

 this experiment is to get the cotton in a soluble modification ; but 

 as ammoniacal oxide of copper diffuses slowly, I must wait a month 

 to obtain a result. It is clear that this experiment could not be 

 made with vegetable parchment, which is acted on by the ammo- 

 niacal copper solvent. 



Experiments were made in which water was replaced by other 

 liquids, such as bisulphide of carbon and oil of turpentine. 



The diffusibility of different crystalloids in bisulphide of carbon is 

 by no means the same in all cases. Thus, if iodine, sulphur, and 

 naphthaline are dissolved in bisulphide, the two latter pass into a 

 porous vessel full of pure bisulphide much sooner than the former. 



If it might be permitted to venture an explanation of the unex- 

 pected phenomena discovered by Mr. Graham, it might be said that 

 parchment-paper or porous vessels act as a kind of sieve, through 

 which the more attenuated molecules pass more readily ; for the 

 colloids have generally a high equivalent and a considerable atomic 

 volume. The opposite is the case with crystalloids ; and the less 

 diffusible of the crystalloids are those which correspond to the greatest 

 atomic volume (taking for this the quotient of the atomic weight by 

 the density, which cannot be exact). Such is iodine, which is less 

 diffusible than sulphur. — Comptes Rendus, Nov. 10, 1862. 



