Ionization by Spraying. 



391 



o£ water, as may be seen also from the curves in figs. 3 

 and 4. 



Another and better method may be adopted. The ionized 

 air may be introduced into the electroscope, which is initially 

 uncharged, and after a stated period the charge may be given 

 and the conductivity of the gases then determined. 



The results obtained were very surprising, and indicated 

 that the spray from benzyl alcohol contained ions which could 

 be stored for considerable periods. The ions were in all 

 cases removed in ten to fifteen minutes after the charge 

 (whether positive or negative) had been given to the central 

 system of the electroscope. 





Total fall of gold leaf 





Charge given 



less corresponding 

 natural leak. 



Per cent. 



Initially 



44 



100 



after 2 minutes. 



23 



52 



„ 5 



17-5 



40 



„ 10 



11-3 



25 



„ 20 



8-0 



18 



„ 30 



6-4 



14 



„ HO 



2-8 



6-3 



,,120 



1-5 



3-4 



Thus the ionization may be measured after the ions have 

 been stored for two hours in a vessel where there is no 

 electric field. 



In a paper to this magazine (September 1906) it has been 

 proved that the <y rays from one gram of radium generate in 

 a zinc vessel at one metre distance about 3 x 10° ions per 

 c.c. per second. I placed 11 mg. of radium at a distance of 

 1 metre from the centre of the electroscope. The radium 

 was screened with lead so that the /3 rays were intercepted. 

 Allowing for the partial absorption of the <y rays by the lead, 

 there would be 3300 ions per c.c. per second generated by 

 the 7 rays, and these, being completely removed by the 

 electric field, gave a gold-leaf deflexion of 24 divisions a 

 minute. This is a simple method of calibrating the electro- 

 scope. Now when the spray from benzyl alcohol is intro- 

 duced into the electroscope the entire removal of the ions, 

 from the time of their formation, over the same part of the 

 scale is equivalent to a fall of 84 divisions. Hence the 

 number of ions initially was 11,200 per c.c. throughout the 

 electroscope. The corresponding value for water spray is 

 about half this, and is in satisfactory agreement with the 

 order of the effect produced by a hand sprayer and measured 



