496 



On Loss of Charge by Evaporation. 



carried off any of the negative charge. The conclusion^, 

 therefore, again is that there has been no loss of charge by 

 evaporation snch as could be detected by this apparatus. 

 We shall consider later what that amount would be. 



A further series of experiments was made corresponding 

 to those just described, but using distilled water and with 

 the surface of the water carrying a positive instead of a 

 negative charge. These, however, gave results in no way 

 different from the above. 



3. Evaporation of Ether. 



To make still further tests on this subject, since those with 

 water had given a different result from that obtained by 

 Pellat, experiments were now made with ether as the evapo- 

 rating liquid. A very rapid evaporation was thus obtained 

 at the ordinary temperature of the room. 



The apparatus used was that of fig. 2, and in the experi- 

 ments made it was found that in the course of an hour, 

 without any heat being applied to the case, the liquid, which 

 at first filled the vessel V, had almost entirely evaporated 

 away. The results of three experiments are given in the 

 following table : — 







Potential of 0. 



Deflexion from zero of 

 Electrometer. 



(*) 



Without Ether. 

 With do. 



+ 146-5 volts. 



+ 4 divs. in 60 m. 

 + 5 „ „ 60 m. 



(6) 



Without Ether. 

 With do. 



+ 147 volts. 



+ 15 divs. in 60 m. 

 +13 „ „ 60 m. 



(o) 



Without Ether. 

 With do. 



- 149 volts. 



+ 1 div. in 60 m. 

 + 2 „ „ 60 m. 



In (c), since the liquid has a positive charge, any loss'of 

 charge due to evaporation should give a negative deflexion. 



Thus even with this rapid evaporation no loss of charge 

 due to evaporation can be detected. 



It only remains to show what loss of charge could be 

 detected by the apparatus used in these experiments. The- 

 capacity of the system shown in fig. 2 was found to be 

 152 C.G.s. units, the increase on that of fig. 1 (viz. 83) being, 



