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LXX. On the Action of Colloids on Radioactive Products in 

 Solution. By T. Godlewski, Ph.D., Professor of Physics, 

 Technical High School, Lemberg (Lwoio)*. 



1. The Radioactive Hydrosols. 



IN a previous paper, " On Solutions of Radioactive 

 Products " f? ^ was shown that the products o£ the 

 active deposit of radium in neutral, alkaline, or weakly 

 acidulated solutions are in the colloidal state. This con- 

 clusion was based upon the results derived from an investi- 

 gation of the electrolysis of aqueous solutions of radium 

 emanation together with its successive products. The 

 experiments established the fact that in acidulated solutions 

 or in presence of polyvalent cations, the said products are 

 deposited at the cathode almost exclusively. On the other 

 hand, in alkaline solutions or in presence of polyvalent 

 anions, it was the anode which first of all was activated by 

 electrolysis. Now precisely this change of sign of the 

 electric charge under the influence of H, OH, or polyvalent 

 ions constitutes the property characteristic % of colloidal 

 suspensions, and it strongly suggests that we are dealing 

 here with a process of the nature of cataphoresis and with 

 colloidal hydrosols. When it is remembered, indeed, that 

 the above-mentioned products are but very sparingly soluble 

 in water, we easily understand that an atom of EaA arising 

 from an atom of emanation dissolved in water, and thus 

 suddenly appearing in a medium which does not dissolve 

 ft a A, will constitute a nucleus for the centre of the distinct 

 phase. In Zsigmondy's § opinion, the most satisfactory 

 method for the production of colloids is to induce reactions 

 from which there shall result the formation of substances 

 which, as crystalloids, are insoluble in the medium. In the 

 case of usual irreversible colloids, e. g. those of metals, 

 this result can be arrived at either by producing a suitable 

 reduction in the liquid medium or by pulverization of the 

 metals attended by a supply of electrical energy (Bredig's 

 or Svedberg's method). In the case of radioactive products, 

 the reaction which produces centra of colloidal suspensions 

 is the radioactive transformation itself, whence new atoms 

 come into being. 



* Communicated by the Author. Presented before the Academy 

 of Sciences in Cracow at the sitting of 5th January, 1914. 



t T. Godlewski, Bull, Intern, de TAcad. d. Sc. de Cracovie, 1913, 

 p. 335 ; Le Radium, 1913, p. 250. 



% Cassuto, ' Der Kolloide Zustand der Materie/ p. 245. 



§ Zsigmondy, ' Kolloidchemie,' p. 2. 



