448 Passage of Electricity through Hot Gases. 



atoms must be neutralized by combining with equal and 

 oppositely charged atoms, or perhaps by acting on atoms 

 quite close to them. In any case, for the charge to diminish 

 there must be atoms in the neighbourhood of the plate. If 

 the electric intensity in the neighbourhood of the plate is 

 sufficient, these may be supplied by the splitting up of the 

 molecules by the electric field, and we have the electric dis- 

 charge ; or the atoms may, as in our experiments, be supplied 

 by the dissociation of the molecules by heat. Besides the 

 mere existence of the atoms, the conditions must be such that 

 they come into intimate contact with those of the metal. 



A possible way of supplying the atoms necessary to get rid 

 of the charge might be by chemical action of the gas on the 

 electrodes. In this case, however, the leak would be much 

 less than if the whole body of the gas contained free atoms, as 

 in the preceding experiments. I tried some experiments on 

 the conductivity of gases which slowly acted on the elec- 

 trodes, and also of mixture of gases, such as chlorine and 

 H 2 S, which slowly act upon each other, these experiments 

 being made at a temperature less than 100° C. I was not able 

 to be sure of any leak by the galvanometer method, and a 

 similar remark applies to an experiment when the electrodes 

 were made white hot while the gas was cold. It must be 

 remembered that the galvanometer method, although more 

 convenient, is not nearly so sensitive as the electrostatic 

 method ; so that these results only show that the conductivity 

 in these cases is not comparable with that of some hot gases. 

 It is known that the leak from a hot platinum wire can be 

 detected with an electroscope. 



The connexion on this view between the conductivity of 

 metals and their tendency to assume the atomic condition, 

 which is exemplified by the abnormal vapour-densities of 

 these substances, will at once occur to the reader. 



Unsaturated Compounds. 

 It is very interesting to see whether the molecules of un- 

 saturated compounds possess the same electrical properties as 

 atoms or not. I accordingly examined the electrical pro- 

 perties of two gases, which on the ordinary electrical theory 

 of chemical action would be unsaturated, viz. NO, and ozone, 

 prepared by passing air through a tube in which the silent 

 discharge was taking place. I could not ascertain that these 

 gases behave in any way differently from air. They transmit 

 electrostatic induction : for example, a gold-leaf electroscope 

 will work perfectly well inside a glass vessel filled with NO 

 or ozone, and the leaves will be attracted by an electrified 

 body outside the electroscope. A current from a battery 

 containing a moderate number of cells will not pass through. 



