1909.] The Dialysis of Colloidal Ferric Hydroxide. 53 



THE DIALYSIS OF COLLOIDAL FERRIC HYDROXIDE. 

 By E. F. Burton, B.A., Ph.D. 



CRead 2jth November, 1909.) 



Some time ago Duclaux (i) published results of his experiments 

 which seemed to throw doubt on the accepted notion of the action of 

 Electrolytes on colloidal solutions. In particular he challenges the work 

 of Hardy (2), which was borne out so well by the previous work of Linder 

 and Picton (3). Duclaux experimented upon colloids which were pro- 

 duced by the action of two salts upon one another, giving an insoluble 

 finely divided suspension : for example, the action of potassium ferro- 

 cyanide on copper chloride producing the insoluble copper ferrocyanide, 

 or the action of bases on ferric chloride producing colloidal ferric hydrox- 

 ide. Duclaux suggested the following law with regard to these reactions: 



"A precipitated colloid, i.e., one capable of giving a colloidal solution 

 in pure water, produced by the mixture of two crystalloidal salts contains 

 the four radicals of the two salts in proportions varying continuously. 

 One must consider them as combined, for they do not react either among 

 themselves, or with the surrounding liquid, according to their ordinary 

 properties." 



In the case of the colloid with which this paper deals, viz., ferric hy- 

 droxide, Duclaux believes that the particle consists of a nucleus corres- 

 ponding to the formula Fe^Cl^.n.Fe^.O^ in which he found n to have a 

 value varying from 30 to 500. The electrical charge possessed by the 

 particle he ascribes to the small part of chlorine, or, perhaps, the ferric 

 chloride, which for that reason he calls the active part of the com- 

 bination making up the colloidal particle. When the colloid is coagulated 

 the action is due to the substitution of some other acid radical for the 

 chlorine ; this action is affected by several circumstances, such as whether 

 the ions producing the coagulation form with the chlorine ions of the 

 particle an insoluble compound or not. Consequently Duclaux doubts 

 the truth of the valency law as perfected by Hardy. In support of his 

 position Duclaux cites experiments carried on with ferric hydroxide, 



(i) Jour, de Chim. Phys. V. i, 2, 3., p. 29. 



(2) Jour, of Physiol. V. XXIX, 1903, p. 26. 



(3) Jour, of Chem. Soc. Vols. LXI. LXVII, LXXI, LXXXVII. 



