Reference : Sur la floculation des milieux troubles
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
Sur la floculation des milieux troubles
[en] Flocculation of Turbid Media
Spring, Walthère [Université de Liège - ULg]
Recueil des Travaux Chimiques des Pays-Bas et de la Belgique. 2e série
[en] Colloids ; Flocculation ; Turbid media
[fr] Colloïdes ; Floculation ; Milieux troubles
[en] Spring, W. Recueil des Travaux Chimiques des Pays-Bas (1900), 19, 204-35 ; SciFinder (Chemical Abstracts Service: Columbus, OH); (accessed July 8, 2010).

This paper commences with an historical summary of the researches of previous observers on liquids rendered turbid by the presence of solid substances in a minute state of division (pseudo-solutions), and a bibliography of the subject is given in an appendix. Details are then given of the author's own experiments, the results of which are summarised as follows. Solutions of salts which, which like those of polyvalent metals, cannot be obtained in an optically transparent condition (Abstr., 1899, ii, 537) bring about the flocculation of turbid liquids much more readily than solutions of any other salts. This result is due partly to the agglutinative power of the metallic hydroxides formed by the hydrolysing action of the water, and partly to the flocculating action of the acids simultaneously produced. The extent of the flocculation caused by hydroxides is closely connected with their chemical and physical character as well as with the nature of the turbidity. The behaviour of the turbidity towards salt solutions somewhat resembles that of a membrane, the acid formed by the hydrolysis of the salt traversing the liquid by diffusion whilst the metallic hydroxide is precipitated with the substance causing the turbidity. The persistence of very fine turbidities bears a relation to the Brownian motion. In consequence of this motion, particles suspended in pure water frequently collide with one another without coming into actual contact, but if an electrolyte is present the particles agglutinate, the Brownian motion ceases, and the flocks formed are deposited. The flocculation of liquids is not brought about by electrical action at a distance, as by Rontgen rays or the electricity developed by a statical machine or an induction coil, and cannot therefore be compared with the precipitation of dust particles in air. The feeblest electric current is, however, sufficient to induce clarification, which in the majority of cases commences at the cathode. Electrolytes of the same conductivity but having different anions and cations influence the flocculation very unequally. Electrolytes having the same cation induce flocculation in equal times, whilst the nature of the anion plays only a secondary part. The rate of flocculation in different electrolytes having the same anion is exactly in the order of the velocities of the cations in electrolysis. It therefore appears that the primary cause of the flocculation brought about by electrolytes is to be sought in the velocities of the ions.

Reprinted with the permission of the American Chemical Society. Copyright © 2010. American Chemical Society (ACS). All Rights Reserved.
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