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111. 



THE NATUEE OF THE IONS PRODUCED BY BUBBLING AIE 

 THROUGH MERCURY. 



By PROFESSOR J. A. M'CLELLAND, D.Sc, F.R.S., 



AKD 



P. J. NOLAN, M.Sc, 

 University College, Dublin. 



Read Fkbkuaky 2S. Published May 18, 1916. 



The allied subjects of the electrification produced by bubbling air through 

 liquids and by splashing and spraying liquids have been frequently 

 investigated in recent years, and some generalizations of importance have 

 been obtained, but there are still much confusion and uncertainty. 



This paper deals with the mobility of the ions carried away by air 

 which has bubbled through mercury, measurements being made both with 

 air containing the normal amount of water-vapour, and also with air well 

 dried. The paper is closely allied to the preceding paper in this volume, 

 which deals with the mobility of ions carried away by air which has been 

 used to spray distilled water, the object of both papers being to obtain 

 further knowledge of the form in which the electrical charge exists. The 

 charge of positive sign remaining on the larger drops when distilled water is 

 sprayed has been carefully examined by J. J. Nolan,* who found that over 

 a considerable range of size of droplets the surface density of charge was 

 constant. 



Apparatus. 



The arrangement of apparatus shown in fig. 1 was adopted. Air was 

 forced by a pump, driven by a motor, through a tightly packed plug of cotton 

 wool A, about 20 cms. long, and 8 sq. cms. in cross-section. The air thus 

 purified passed through a glass nozzle immersed in the mercury in a glass 

 cylinder £, which was 30 cms. high, and 8 cms. in diameter. 



In most of the experiments the nozzle through wliich the air escaped 

 was turned up as shown in the figure, and an iron plate was placed above 



' Electrification of Water by Splashing and Spraying. Proc. Roy. Society, A, 

 vol. xc, 1914. 



