288 Wellisch — Experiments on Active Deposit of Radium. 



by the deposit particle at the moment of formation ; what is 

 here asserted is that the particles are uncharged in ether at the 

 end of their recoil path even in the presence of electric fields 

 which are easily able to prevent recombination of the gaseous 

 ions. 



It is probable that if the concentration of the emanation 

 were sufficiently great the deposit particles in ether would 

 form positively and negatively charged aggregates, as has been 

 shown later (section 5) to occur for the deposit particles in air. 



Distribution of Active Deposit in Air, Hydrogen and Carbon 



Dioxide. 



4. A slight correction has to be made for the limiting 

 values of the cathode deposit in air, hydrogen and carbon 

 dioxide, owing to the fact that in the previous paper the diffu- 

 sion correction was made on the assumption that the diffusion 

 distribution was proportional to the areas of the exposed sur- 

 faces. The experimental values (p) uncorrected for the diffu- 

 sion of neutral particles, which were obtained for the percentage 

 cathode deposit, were as follows : air 89*4, H 2 89*4, C0 2 81*1. 



The corrected values, which give the number of positive 

 particles expressed as a percentage of the total number of par- 

 ticles, are obtained by evaluating the expression ~- — . 



j. / y 



These values are : air 88'2, H 2 88-2, C0 2 78-9. 



The broken curves given in fig. 2 of the previous paper, 

 which exhibit the dependence of the cathode deposit on the 

 amount of emanation when small potentials are applied to the 

 case, would take slightly different positions if the proper diffu- 

 sion correction were made. The effect of this correction 

 would be to make each activity curve lie still further below 

 the corresponding ionization curve than it actually does in the 

 diagram ; this would bring out, with greater emphasis than 

 before, the fact that the rate of recombination between the 

 positively charged deposit particles and negative ions is greater 

 than between the positive and negative ions among themselves. 

 Inasmuch as this point is brought out clearly by the curves 

 there given, and as, in any case, the actual shape of any one of 

 the curves depends upon the particular vessel employed, it was 

 not thought desirable to reproduce the corrected curves. 



Experiments with large Amounts of Emanation. 



5. It was shown in Section 3 that when the emanation mixed 

 with any gas is introduced into a cylindrical vessel the amount 



