58 



S. G. LUSBY. 



without mechanical filtration, the depth of the stream being 

 0*5 cm. The drying agents were tested for any ionising 

 action on air in contact with them, but without any effect 

 being detected. 



The percentage of moisture absorbed during the passage 

 of the air over the hygroscopic material, was estimated 

 from the results of independent experiments giving the 

 amount of water absorbed by phosphorus pentoxide, in test 

 tubes in series, from the air as it emerged from the testing 

 pipe. The percentages of moisture absorbed, given in 

 Tables II and III are calculated on the assumption that 

 the air was 'quite dry' after passing the final test tube. 



The percentage reduction in the number of ions was 

 determined by measuring the ionisation in natural air, and, 

 immediately afterwards, in air, from the same source, which 

 had passed over the drying agent. For the experiments in 

 connection with the small ions the shorter section of the 

 electrode of the testing pipe was connected to the electro- 

 meter. 



Table II — Absorption of small ions. 



Absorbing Material. 



Percentage of moisture 



absorbed on assumptiou 



previously stated. 



Percentag-e 

 number 



+ 



reduction in 

 of ions. 



Number 



of 



trials. 



CaCl 2 in tube 

 P 2 6 in tray 



50 



96 



29 

 50 



29 



50 



6 

 4 



Table III — Absorption of large ions. 



Absorbing Material. 



CaCl 2 in tube 

 P 2 5 in tray 

 P 2 5 in tray 

 + two test tubes 



Percentage of moisture 



absorbed on assumption 



previously stated. 



50 



96 



'quite dry 



Percentage 

 number 



+ 



reduction in 

 of ions. 



Number 



of 



trials. 



24 



29 



12 



46 



46 



6 



56 



55 



3 



