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1[. 



THE MOBILITIES OF IONS PEODUCED BY SPRAYING 

 DISTILLED WATER. 



By J. J. NOLAN, M.A., M.Sc, 

 University College, Dublin. 



Read Februauv 28. Published May 18, 1916. 



In a previous paper* the electrification given to distilled water by breaking 

 it up in contact with air has been investigated. It was found that the water 

 took up a positive charge which was proportional to the area of new water- 

 surface produced. The breaking up of the water was produced in two ways : 

 (1) by allowing drops to splash against an air-blast, and (2) by spraying. 

 Concordant results were obtained from these methods, the values of the charge 

 produced per square centimetre of new surface in each case being identical. 

 The negative charge is carried off in the air, which contains ions of both signs, 

 negative being in excess. A knowledge of the nature of this ionisation would 

 be of importance in any attempt to formulate a theory of the effect. The 

 experiments described in this paper have, therefore, been undertaken. A 

 short account of some of the results has been given already in the previous 

 paper. A more complete account can now be given. 



Investigations bearing on these experiments have been made by Kahler.f 

 Aselmann,J and Simpson. | Kahler found that when distilled water is splashed 

 negative ions only are produced. Aselrnann also, working under similar 

 conditions, found only negative ions. These ions had mobilities lying over a 

 wide range. Limiting values of mobilities were obtained, the highest mobility 

 and the lowest being respectively 4 cm. /sec, and 2'7 x 10'* cm/sec, in a field 

 of 1 volt per cm. Very few of the ions, however, had mobilities lower than 

 1-6 X 10"- cm/sec. Simpson found that when distilled water is broken up in 

 air, ions of both signs are produced, negative being in e.Kcess. No measure- 

 ments of mobility were made. 



* Nolan. Proo.Roy. Soc, vol. xc, p. 531 (1914). 

 t Kahler. Ann. der Phys., vol. xii, p. 1119 (1903). 

 X Aselrnann. Ann. der Phys., vol. xix, p. 960 (1906). 

 § Simpson. Phil. Trans., vol, ccix, p. 379 (1909). 



K.I.A. PROC, VOL. XXXm., SECT. A. [2] 



