580 



sulphide by filtration; removal of the residue of sulpluireted hydrogen 

 by boiling the filtrate. 



A second precipitate is generated by adding to the filtrate some 

 drops of ferro-chloride solution and afterwards an excess of ammonia; 

 this precipitate of iron hydroxyd is filtered off again after some 

 hours; this process is repealed three times. 



Lastly a third precipitate is generated by adding barium chloride 

 at boiling heat; next day the precipitate is filtered off; this process 

 is repealed under an excess of sulphuric acid, so that all (he barium 

 is precipitated; now the filtrate contains a small amount of caesium 

 sulphate over and above all the original caesium chloride. 



This pi'ocedure serves to remove a heavy radio-active element, 

 which is left behind in the precipitate. 



Originally the caesium-salts we used contained some of this 

 impuiity. If the dosis is high enough then there will be enough of 

 the impurity to pi'oduce a biological action such as we may expect 

 of a radio-active substance. 



This biological action hus the nature of a beta-radiator as is 

 obvious from the antagonism of our caesium to uranium. Miss L. Kaiskr 

 has recorded some instances of Cs-Uequilibria. * 



We annex a recent instance. 



kloppen = beat 



Fig. 2. 



A frog's heart beats initially on a Ringer solution, which contains 

 per Liter instead of potassium JO mgr. of uranyl nitrate. By adding 

 to this solution a quantity of 1500 mgrms of Caesium-chloride a 

 radio-physiological equilibrium is engendered between the alpha- 

 radiator uranium and the beta-radiator caesium. A standstill corres- 

 ponds with this equilibrium in which there is not even latent auto- 

 maticity. However, directly when we increase the quantity of caesium, 

 a caesium beat is developed. Another equilibrium will then again 

 be called forth by increasing the quantity of uranium, which now 

 is on a higher level, because more has been taken of the two 



