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V. On Electrifications due to the Contact of Gases with 

 By J. Enright, B.Sc* 



A STUDY of HelmhohVs theory of atomic charges led 

 to the experiments I am about to describe. When one 

 has got the idea that molecules are kept in their integrity by 

 the mutual attractions of the oppositely charged atoms or 

 radicals composing them, a question soon arises as to what 

 part, if any, these charges play in ordinary chemical reactions. 

 The theory precludes any other form of chemical affinity 

 than that due to the mutual attractions of the opposite 

 charges, and it occurred to me that since at the moment of 

 reaction there must be disturbance and re-arrangement of 

 them, some indication of their existence might be obtained 

 by allowing reactions to go on in an insulated vessel properly 

 connected with a quadrant-electrometer. Even if a per- 

 manent electrification could not follow, I thought it just 

 possible that a momentary flutter of the " spot " might take 

 place on account of the electric disturbance due to the inter- 

 change of the charged ions. 



This consideration alone was sufficient to excite one to 

 experiment, but if I tell the whole story I must say that I 

 had had other expectations. According to theory the charges 

 on monads are exactly equal. How then does it happen, if 

 reactions be a result of the charges, that chlorine drives iodine 

 out of potassic iodide ? How, indeed, does it happen that 

 any one molecule composed of a particular pair of monad 

 elements is stronger, — that is to say, more stable than any 

 other molecule composed of any other pair of monads ? And 

 so on. After pondering on such questions for some time, I 

 could not suppress the thought that after all perhaps the 

 charges might not be equal, and that the experiments I had 

 determined to carry out might possibly throw some light on 

 the matter. 



Then there were certain special reactions which appeared 

 to afford an admirable opportunity for experimental study of 

 the theory. I refer to cases in which the atomicity of ele- 

 ments undergoes a change during a reaction, 



2Fe II S0 4 + H 2 S0 4 + Cl 2 = Fe 2 IV (S0 4 ) 3 + 2HC1 (Roscoe). 



Here four monad charges of positive electricity attached 

 to the iron on the left change into eight monad charges on 

 the same quantity of iron on the right. If the increment of 

 positive electricity be produced by contact an equal charge of 



* Communicated by the Physical Society : read November 15, 1889. 



