Active Deposit of Radium in Electric Fields. 543 



surface were removed by warming the electrodes in a 

 bunsen flame. The electrodes were almost exactly the same 

 size in each case, so only a slight correction was required to 

 the observed values. This was obtained from the curve in 

 fig. 3. The corrected values are given in the following 

 table; the number of individual observations in each case 

 was about ten. 



1-000 Standard. 

 0-921 ±0-031 

 1-068±0014 

 1-000 +0-024 



The results show that the nature of the metal has very 

 little influence on the value of the anode activity. The 

 variations in the case of the metals used, which are fairly 

 representative, are of the order of 5 per cent, of the anode 

 activity, and this, employing wires of two millimetres 

 diameter, represents changes of a tenth of a percent, in 

 the cathode deposit. There is probably a real effect of this 

 order of magnitude, which is directly due to emanation 

 absorbed by the metal, and the values obtained are probably 

 in the order of the relative absorptive powers of the metals. 

 Little is known about the absorption of radium emanation by 

 metals. The etfect has been demonstrated both by Curie & 

 Danne * and by Rutherford f, who showed that if metals are 

 placed in an atmosphere containing emanation, they liberate 

 absorbed emanation alter removal. This liberation was 

 found to be most persistent in the case of lead, which obser- 

 vation is in agreement with the above results, showing that 

 in this case the rate of diffusion of emanation in lead is very 

 small ; whereas in the case of aluminium it was least per- 

 sistent, where the diffusion must be quicker. 



On the whole the observations indicate that there is a 

 very small effect attributable to absorbed emanation, but it 

 is quite insufficient to account for the anode activity. The 

 evidence does not support the view that the anode activitv is 

 due to a surface condensation of the emanation on the metals, 

 such as occurs, for example, in the case of oxygen on 

 platinum. We can deduce the order of magnitude of the 

 concentration necessary on this hypothesis to account for the 



* Curie & Darrne, C. R. cxxxvi. p. 364 (1903). 

 t Kutherford, Phil. Mag. Nov. 1904. 



