314 Electrification at Liquid" Gas Surfaces* 



that a progressive change in the concentration at the surface 

 takes place as the bubble gets smaller. The surface layer 

 first formed adsorbs a certain amount of salt which it 

 apparently retains as it gets smaller, thus increasing the 

 concentration. As in Metcalf's experiments no difference 

 could be observed between the action of hydrogen and 

 oxygen in this case. 



This view of the action of the gas in these experiments is 

 merely an hypothesis, and the work is being continued with 

 the object of rinding out more accurately the part played by 

 the gas and by the salts dissolved in the liquid* 



Summary. 



A rotating cell method of examining the electric charge on 

 small spheres of gas in a liquid has been worked out. 



Quincke's observations on the movement to the positive 

 pole of small spheres of air, oxygen, and hydrogen in distilled 

 Wafer were repeated, using the rotating cell. 



The velocity of small spheres of gas in water was found to 

 be proportional to the potential gradient and independent of 

 their size (within limits). 



The velocity of spheres of air, oxygen, and hydrogen in 

 water was found to be about 4 , 10 ~ 4 cm./sec/volt/cm. 



Dissolved salts affect the charge at a gas-liquid surface, 

 the activity of the salt depending on the charge carried by 

 its ions in solution. 



An air-water surface^ — in the absence of polyvalent ions — 

 is electrically neutral in a slightly acid solution. 



A sphere of gas in a solution can change the sig;n of its 

 charge as it diminishes in size, by being absorbed into the 

 solution. 



Under the conditions of these experiments the electric 

 charge at a liquid-gas surface appears to be almost inde- 

 pendent of the nature of the gas. 



My best thanks are due to ProFessor Sir J. J. Thomson for 

 suggesting this research and for his kind advice during the 

 progress of the work. 



