350 Prof. J. J. Thomson on the 



Effect of Temperature upon the Amount of Electricity 



produced. 



The electrification produced by drops of distilled water in- 

 creases as the temperature increases ; this is shown by the 

 following measurements made at different temperatures :— 



Temperature. Deflexion. 



15°C 230+ 



75° 390+ 



95° 420+ 



The effect of temperature upon a solution of rosaniline is 

 very remarkable. At first increase of temperature produces 

 an increase in the electrification, but on increasing the 

 temperature still further the electrification diminishes and 

 finally changes sign. The deflexions due to a rosaniline solu- 

 tion are given in the following table : — 



Temperature. Deflexion. 



15°C 180- 



70° O 260- 



75°C 120- 



90°0 20 + 



95°C 40+ 



Effect of Altering the Gas surrounding the Drops. 



I have already alluded to the reversal of the electrifi- 

 cation of drops of distilled water which takes place when 

 hydrogen is substituted for air. If in place of distilled water 

 we use dilute solutions of different substances, we find that the 

 effect of substituting hydrogen for air depends very much 

 upon the nature of the solution. Solutions such as those of 

 phenol, pyrogallic acid, fluorescene, whose drops are electrified 

 in the same way as those of distilled water, are affected by 

 hydrogen in the same way as the drops of water are affected; 

 *'. e., the positive electrification which the drop possesses in air 

 is in hydrogen exchanged for a small negative electrification. 

 On the other hand, the effect of substituting hydrogen for air 

 in the case of substances like methyl violet, rosaniline, potas- 

 sium permanganate, whose drops show a negative electrifica- 

 tion in air, is to increase this negative electrification, and the 

 deflexion of the electrometer is greater when the drops fall 

 through hydrogen than when they fall through air. 



