220 Bar us — Ionization of Water and Phosphorus Nuclei. 



is then independent of the one used for water nuclei, the latter 

 being not applicable to phosphorus at all. It is obvious, how- 

 ever, that in the light of the experience now gained,, a com- 

 plete repetition of the experiments is desirable, since in tubular 

 condensers there is necessarily undersaturation, the effect of 

 which is to decrease n . 



Unfortunately the coronas are not as directly available with 

 the phosphorus emanation as with water nuclei ; for while the 

 condenser determines the nucleation of the air immediately 

 after it has passed over phosphorus, condensation can only be 

 produced in vessels in which the nucleation is either dilute 

 (small charge of emanation added to a large bulk of air), or is 

 stale, while the initial coronas are mere fogs. Thus the pro- 

 cedure carried out for water nuclei fails for phosphorus, but I 

 shall show in a succeeding paper how it may be supplemented, 

 and that the data of a purely optical method are of the order 

 of those just found from a purely electrical method. 



5. The question now arises whether the effect of a Held in 

 removing nuclei more or less completely may be explained. If 

 U= e/67r/jLjR, the current will be, per square centimeter, 



._E ne> 



X 67r/xi? 



where E/x is the potential gradient. For the same current in 

 the unit field, ne*/fifi = ne V/jul — constant, or the number of 

 nuclei needed will depend inversely on the square of their 

 charges and directly on their radii ; or in a given medium will 

 depend inversely on the energy of their charge. 



The question takes rather a different form, inasmuch as it is 

 of interest to know how the number of charges removed by 

 the field compares with the total number present in and added 

 from without to the medium during this interval. The case 

 may be worked out for the cylindrical condenser, as above. 



If time losses of nuclei and charges other than are due to 

 absorption at the walls of the vessel be ignored, and if n nuclei 

 are present at the section 1=0 and n at the section I of the 

 condenser, 



27rfcZ(r 2 + r, ) 

 n — n o e 16-7 V 



In the absence of the field this equation determines the spon- 

 taneous loss of charges whether the nuclei are spontaneously 

 lost or not; but in the presence of a field the charges are 

 more rapidly removed because of the added velocity imparted 

 to the nuclei. Moreover for water nuclei, k may usually be 

 neglected in comparison with UE/ir^—r^). In other words, 

 K= UE/(r 2 -?\\ and 



