770 Sir J. J. Thomson on the 



around AB was sufficient to drag some o£ these molecules up 

 to either A or B or to both of them, producing a more 

 complex system. The proximity of these molecules to A and B 

 would increase the capacity of the system, and would therefore 

 facilitate the passage of a corpuscle from one atom to another, 

 so that these atoms might get charged in presence of these 

 molecules, whereas if they were alone they might remain 

 uncharged. 



Another way of considering the effect produced by the 

 other molecules is illustrated by fig. 1. A and B are atoms 



Fig. 1. 

 M, A B M 2 



©O ©©(DO 



each containing one corpuscle. The force tending to make 

 the corpuscle in A leave it and pass over to B is the attraction 

 of the doublet in B ; the force preventing it is the attraction 

 of the positive charge, which may for simplicity be supposed 

 to act at the centre of A. We see from the figure that when 

 the molecules M l5 M 2 containing doublets join on to A and B, 

 their effect is to diminish the attraction holding the corpuscle 

 in A to that atom, and to increase the force tending to pull 

 it out ; each of these effects will promote the escape of the 

 corpuscle from A. 



A very striking example of the effect of attached molecules 

 in promoting intra-molecular ionization is afforded by the 

 platino-ammino chlorides studied by Werner (Werner's ' New 

 Ideas on Inorganic Chemistry,' English translation, p. 41). 

 The compound PtCl 4 (NH 3 ) 2 is not an electrolyte : when, 

 however, another molecule of ammonia is attached, giving 

 the compound PtCl 4 (NH 3 ) 3 , it becomes an electrolyte with a 

 molecular conductivity of 96*75 ; when it takes up another 

 molecule of ammonia and becomes PtCl 4 (NH 3 > ) 4 , the mole- 

 cular conductivity rises to 228 ; while two more molecules 

 of ammonia produce PtCl 4 (NH 3 ) 6 , ane lectrolyte with a 

 molecular conductivity of 522*9. We may regard the 

 acquisition of electrolytic conductivity as evidence that by 

 the addition of ammonia one or more of the chlorine atoms 

 in the salt have been able to attract corpuscles probably 

 from the platinum atom. 



Let us first consider the conditions necessary for the 

 occurrence of intra-molecular ionization. 



(1) There must be a considerable difference in the electro- 

 chemical properties of the atoms A and B, to furnish the 



