168 MM. Elster and Geitel on 



platinum, which were introduced into the apex of a pure- 

 alcohol flame. In the gas-flame there was always a fusion of 

 the aluminium, altering the shape of the electrode. The pos- 

 sible source of error herein contained also disappears when a 

 spirit-flame is employed. The determinations of the electro- 

 motive force of the flame were: — when its apex was conducted- 

 from by 



The platinum plate . . 1201 

 The copper plate . . . 166'0 

 The aluminium plate . 301 "5 



Sodium and magnesium are more negative than aluminium, 

 as will be seen from the following numbers: — 



Flame conduc'ted-from by Electromotive force. 



Platinum wire 119 



Aluminium wire 198 



Magnesium ribbon .... 221 

 Sodium 338 



The last two metals were introduced into the lower part of 

 the flame, in order to prevent their ignition. The sodium was 

 a piece of the size of a bean, with a bright cut surface. 



The relative position to one another of all the metals em- 

 ployed is specified by the following numbers : — 

 f Gold (not pure) 1 

 I Platinum }> , . 150 



I Silver (not pure) J 



Purchased wires of ■{ Iron ■ . 170 



I Copper ...... 200 



I Aluminium ...... 300 



[Magnesium 320 



Sodium 500 



A Daniell's element =100 



It is consequently put beyond question that the electric 

 condition of a flame depends essentially upon the nature of the 

 metal conducting from it ; but that nevertheless the quality 

 of the surface of the electrode which is in air plays also an 

 essential part was evidenced by the following experiments: — 



If the insulated base-electrode in air be wetted with water 

 or a salt-solution while the apex of the flame communicates 

 with the earth, a very considerable diminution of the electro- 

 motive force immediately takes place, especially when a solu- 

 tion of potassium chloride is employed. 



A perfectly clean platinum wire, employed as the base- 

 electrode, gave E = 184; when it was wetted with distilled 

 water, E instantly fell to 134, passed through the values 148, 



