Electrification at Liquid- Gas Surfaces. 



305 



Al (N0 3 ) 3 16 H,0. 



Time. 



Charge. 





Seconds. 





10~ 9 .4 



40 



- 



10" 9 .8 



67 



- 



10" 8 .2-4 



slow 



+ 



10~ 8 .4 



,1 



+ 



10~ 7 .4 



faster 



+ 



10" 6 „2 



„ 



+ 



Or (N0 3 ) 3 18 H 2 0. 



Time. 



Charge. 





Seconds. 





10~ 9 .4 



20 



- 



10~ 8 .2 



28 



- 



10" 8 .4 



34 



- 



10~ 7 .l-2 



50 



— 



10 _7 .4 



80 



— 



10" 7 .8 



slow 



- 



The first two salts reverse the sign of the charge on a 

 water-air surface, and it seems likely that the chromium salt 

 would have done the same if the concentration could have 

 been made a little greater. 



The following tetravalent nitrates were then tried : — 



Th (N0 3 ) 4 12 11,0. 



Time. 



Charge. 





Seconds. 





10- n .7 



26 



- 



10- 10 .7 



77 



•f 



10- 9 .7 



57 



+ 



10~ 8 .l-4 



48 



+ 



10 _S .2-8 



40 



+ 



Phil Mag. S. 6. Vol. 27. No. 158. Feb. 1914. 



X 



