[ 38 ] 



IV. 



THE NAXrUE OF THE lOXS PEODUCED IX Mil BY EADIO- 



ACTIVE BODIES. 



Uy rj;OFESS()l! J. .1. NOLAN, ,M.A., D.Su., 

 University College, Dublin. 



Rend NovKMiiKU 8. I'liblislied Dbckmhkk ;!0, 1920. 



In an e.xaminatiou of the ionization produced by spraying water,^ the author 

 obtained evidence of the existence of a j^rcat variety of ions, some of them of 

 mobility much greater than that ordinarily attributed to the small ion in 

 air. On a more complete examination it was found- that several groups of 

 such mobile ions existed, some of very high mobility. In addition, aniinibcr 

 of other groups were separated out, the mobilities of wliicli roughly 

 correspondeil lo those observed for ions produced in air by the ordinary 

 ionizing radiations. Four sucli groups were specially noted. These groups 

 contained ions having for mobility in unit field (volt/cm.) the values 

 1'94, 1-70, r49, and 1";34 cm/sec. respectively. It was suggested: (1) that 

 all these ions consist of clusters of water-molecules of diflcrent sizes, the very 

 mobile ions corresponding to the very small groups (one, two, three 

 molecules, etc.), and tlie othere, such as the four mentioned above, consisting 

 of hunger groups of a regularly graduated size ; (2) tliat the ordinary small 

 ion in air and otlier gases is also a stable cluster of water-molecules, identical 

 with one or other of the four forms mentioned above, the particular form 

 prevailing at any time depending on the sign of the charge, and also on the 

 degree of liuniidity. 



As a first step towards the testing of these hypotheses, the author 

 considered it desirable to make some attempt at an accurate redetermination 

 of the mobility of the ordinary small ion in air of different degrees of 

 humidity. The method employed for the measurement of mobility was 

 practically the .same as lliat devise<l for the measureiuent of llie mobile 

 spray-ions. 



' Proc. Royal Irish Academy, vol. xxxiii (A), p. 9(1916). 

 * Froc. Royal Society, A, vol. xciv, p. 112 (1918). 



