Electrification of the Atmosphere. 153 



§11. Conclusions. 



1. The following substances, common salt, lithium chloride- 

 potassium bichromate, on which iodine or bromine has been 

 sprinkled, have, in the presence of zinc, the property of causing the 

 surrounding atmosphere of air. oxygen, nitrogen, carbonic acid or 

 coal gas to become electrified positively when raised to a temperature 

 l)etween 3oo°C. and 35o°C. An atmosphere of hydrogen is nor 

 electrified in similar circumstances. Stress is to be laid on the fact 

 that it is the atmosphere, not the solid particles, nor the ozone, 

 nor the water vapour which takes the electrification. The electrifi- 

 cation is not due to a gas coming off as it is in the case of potassium 

 permanganate. 



2. The effect differs from the electrification produced by phos- 

 phorus, rontgen rays, uranium, or thorium in that it is only possi'.ile 

 to electrify the gas positively with voltages up to -r 200 volts. 



3. The effect differs from that produced in a red hot iron or 

 copj)er tube in that it does not appear to be due to oxidation or 

 deoxidation. 



4. The atmosphere under the action of these substances brings, 

 about an equalization of potential between two mutually insulated 

 different metals ; in other words, when the two mutually insulated 

 metals are connected by a wire the circuit is completed by the 

 intervening atmosphere, and a current flows. 



5. Other sub.stances which have this property are potassium 

 iodide, treated with bromine, in the presence of zinc, zinc sulphide- 

 zinc chloride, and a number of substances mentioned in §4. 



6. The effect does not seem to be connected with fluorescence, 

 thermoluminescence, or with the giving off of a gas on heating. 



7. There seems to be three distinct methods — apart altogether 

 from the well-known electrifying properties of flames and their fumes- 

 — of obtaining an electrified gas by heating. 



1. By oxidation or by deoxidation as in the atmosphere drawn 



from the neighbourhood of an oxidising or deoxidising 

 metal. (Schuster.) 



2. By driving off from a solid a gas which carries a charge 



with it as in the gas obtained by heating potassium 

 permanganate. (Townsend.) 



3. By heating the atmosphere over iodined common salt — 



and other iodined or bromined substances mentioned 

 above — in the presence of zinc; or by heating the 

 atmosphere in the presence of a number of substances. 

 such as zinc chloride, zinc sulphide. 



