Atom and the Charge of Electricity carried by it. 527 



by the author (Proc. Oamb. Phil. Soc. vol. viii. p. 258). 

 These experiments showed that when a mixture of H and CI 

 was combining it did not possess any conductivity, thus proving 

 that in these cases no charged atoms were set free during 

 the combination. Some other cases of chemical combination 

 gave the same result ; on the other hand there were a class 

 of cases in which ihe mixture of gases acted as a conductor 

 whilst chemical combination was going on. The experiments 

 thus proved that in many cases of chemical combination no 

 charged atoms are set free. 



I also investigated this point by another method. Let us 

 assume for a moment that free charged atoms are liberated 

 during chemical action. To fix our ideas, let us take the case 

 of a piece of zinc attacked by chlorine ; suppose now that we 

 electrify the zinc : if chemical action liberated free ions, or, 

 supposing that an aggregation of atoms is necessary, if the 

 algebraical sum of the charges on the atoms forming this 

 aggregate were not zero, then when the electrified zinc atom 

 enters into chemical combination an atom of chlorine must be 

 set free carrying a charge of electricity of the same sign as 

 that on the electrified zinc atom. Thus, in this case the 

 charge would leak from the metal into the gas and the latter 

 would cease to insulate. If, on the other hand, chemical 

 combination went on between an aggregate of atoms the 

 algebraical sum of whose charges was zero, then, however 

 much the zinc was attacked, there would be no liberation 

 of charged atoms and no transference of electricity from the 

 metal to the gas. 



1 made an extensive series of experiments to find out 

 whether an electrified metal plate when immersed in a gas 

 by which it was chemically attacked did or did not lose its 

 charge. I was never able to trace any leakage of electricity 

 to this cause, even though two metal plates charged to a great 

 difference of potential, either by a Wimshurst machine or by 

 a battery of 2000 small storage-cells, were placed close 

 together in the gas. The electrified surfaces w T ere zinc, 

 mercury, and electrolytic solutions, the gases chlorine and 

 nitrosyl chloride ; but though the conditions of the surfaces 

 showed that active chemical action had taken place, there was 

 no escape of electricity through the gas whether the surfaces 

 were positively or negatively electrified. In these cases the 

 chemical combination went on at the temperature of the room 

 when there was no chance of the gas being dissociated. In the 

 case of combination at very high temperatures, when the gas 

 may be dissociated, we shall see later that there are cases where 

 chemical combination does promote the discharge of electricity . 



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