88 COLLOIDS IN BIOLOGY AND MEDICINE 



GODLEWSKI * found upon electrolysis of the radium emanations and 

 their products that the radioactive substances migrated mostly to 

 the cathode in acid solutions and to the anode in alkaline solutions. 

 PANETH dialyzed a solution of radio-lead nitrate against pure water 

 in a parchment thimble and greatly concentrated the RaE and 

 polonium in the thimble but the relation between RaD to lead was 

 not changed. Both phenomena are characteristic of colloids and 

 indicate the colloid properties of radioactive substances; this led 

 them to continue their investigations. GODLEWSKI * successfully 

 adsorbed RaA, RaB and RaC with inorganic colloids and concen- 

 trated the radioactive substances by precipitating the latter. He 

 was successful not only with radium but with actinium, mesothorium 

 and uranium. The concentration of radioactive substances by 

 adsorption on colloidal silicic acid (EBLER, FELLNER) has attained 

 great practical value in the manufacture of radium preparations. 

 In fact RaA and RaC may be collected from acid solutions simply 

 on filter paper and by burning the paper a highly active ash, free from 

 RaB, may be obtained. It is evident that in solution radioactive 

 elements undergo hydrolysis with the formation of a colloidal radio- 

 hydrosol, 



