250 



J. M. Leivis : 



The platinum wire at B has a fine copper wire soldered to> 

 it, which is led away to a potentiometer. In experimenting with 

 the electrode, the writer was led to make several modifications 

 in its construction. In the first place, it was found that in platin- 

 ising- the electrode, the resistance of the solution in the fine 

 part of the tube was a disadvantage. To obviate this, the 

 writer sealed what may be termed an " inert electrode " into the 

 tube at A. This is used only during platinising, constituting 

 the anode in the system, and the arrangement, when used with 

 a platinising vessel, to be described later, makes for convenience 

 and ease of operation. 



Another modified electrode is shown in Figure 8, which, in 

 this case is provided with two hydrogen electrodes, and one inert 

 electrode. It is thus possible to compare the e.m.f.'s of two 

 electrodes simultaneously placed in the solution under examina- 

 tion, and with it one learns how easily an incorrect reading may 

 be given by an electrode which, to all appearances, is properly 

 platinised, and is in good working order. 



/ \ 



a.--- 



± 



..&■ 



Fig. 8. 



