418 Prof. E. M. Wellisch : Experiments on 



particles are either positively charged or neutral ; it became 

 o£ interest to ascertain whether negatively charged particles 

 were present when the emanation was mixed with ether. 

 This was the immediate purpose of the present investigation, 

 but, as will be seen later, the field was greatly extended as 

 the experiment progressed. 



Experimental procedure. 



2. It is unnecessary to enter here into any detailed 

 description of the apparatus and the experimental method as 

 these were in all respects the same as previously described. 

 The essential features of the method were as follows : the 

 emanation mixed with any gas was introduced into a cylin- 

 drical vessel with a central electrode, and remained there 

 under the desired conditions of potential, pressure, etc., until 

 radioactive equilibrium was established. The emanation was 

 then blown out by means of a strong current of air and the 

 amounts of active deposit on the central electrode and on the 

 case were measured separately, the proper corrections being 

 made for the decay of the deposit after the emanation had 

 been removed. The ionization currents were measured by 

 means of an electrometer which had a sensitiveness of 

 180 mm. per volt. Arrangements were made for the addi- 

 tion of suitable capacities when the currents were large. 



Distribution of the Active Deposit in Ethyl Ether. 



3. In this series of experiments the vapour was obtained 

 by evaporation from the liquid ; it was dried by phosphorus 

 pentoxide and admitted into the testing vessel, which had 

 previously been evacuated. The ether was then removed till 

 the pressure in the vessel was only a few mm., a fresh lot of 

 ether was introduced as before, and this process of fractiona- 

 tion was repeated about five times. In the final stage the 

 «ther was introduced through the radium solution, and after 

 passage through the drying agent was admitted into the 

 testing vessel. 



The following table exhibits the results obtained for the 

 distribution of the active deposit for various pressures of the 

 «ther and for different potentials applied to the case of the 

 testing vessel. 



The results show that the application of either a positive 

 or a negative potential is without any decided effect on the 

 distribution of the active deposit. In the experiments de- 

 scribed in the previous paper approximately the same value 

 was obtained for the deposit on the central rod as in the 



