Loss of Charge by Evaporation. 



495 



order, however, to show the effect of the flame a double set 

 of readings is given in experiment (1) in the table below ; 

 the first set was taken while the flame was present and the 

 water was being heated up, the second set was taken after 

 the flame had been extinguished and the water left to cool. 

 Between these two sets of readings the quadrants of the 

 electrometer were of course connected together so as to start 

 the second set from the zero-point of the scale. It will be 

 seen that in both sets the deflexion obtained with water in 

 the vessel is practically the same as that obtained with the 

 vessel empty. In other experiments, however, this first set 

 of readings was omitted, as so large a deflexion due to an 

 outside cause might give rise to ambiguity. 



In some experiments, instead of heating up the water in 

 the case, the water was boiled apart over a separate Bunsen 

 flame, while the case with its lid in position Avas heated up 

 by its own Bunsen flame till a temperature of over 100° C. 

 was obtained inside the case. The boiling water was then 

 introduced quickly, the lid replaced and connexion made 

 with the battery, and then when the flame was extinguished 

 a set of readings could be commenced. 



The following table gives the results of three experiments. 

 The double set of readings in experiment (1) has been already 

 explained. 



No. of 

 Experi- 

 ment. 



Potential 

 of C. 



Deflexion from zero of Electrometer. 





While heating. 



While cooling. 



(1) 



f- 144- volts. 



Without Water. 

 With do. 



+107divs.in40m. 



+ 111 „ „ 40 m. 



+ 13divs. in 40 in. 

 + 13 „ „ 40m. 



(2) 



+ 150 volts. 



Without Water. 

 With do. 



+26 divs. in 50 m. 

 + 24 „ „ 50 m. 



(3) 



+150 volts. 



Without Water. 

 With do. 



+23 divs. in 50 m. 

 +22 „ „ 50 m. 



In these experiments, omitting the readings while heating 

 in experiment (1), it will be seen that in no case was the 

 positive deflexion greater when water was present in V than 

 when V was empty ; but it should be greater if the vapour 



2M2 



