496 Potential Differences determined by Null Solutions. 
The electrocapillary curves for the null solutions of KI 
and of KOH are shown in fig. 5. 
\ 
■>^ 
Jt 
OH 
\ 
\ 
\ 
\ 
\| 
j \ 
3 
Afifilieot 
t.M.Fs 
■ /coo - c 
■/J 6 /*((-; 

2i 
'00 
s 
too 
7SQ0 
# 
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The results of our experiments may be summarized as 
follows : — 
§ 21. Summary of Conclusions. 
1. The potential-differences between different null solutions 
and mercury are not the same. This is proved, allowing for 
the contact p.d. between electrolytes, by measuring each 
p.d. against the p.d. Hg | KC1, and also by measuring one 
null solution against another. The result is also deducible 
from the electrocapillary curves alone, without introduction 
of the question of the p.d. between electrolytes. 
2. If the null-solution potential-differences are assumed to 
be zero, the values obtained for the p.d. Hg | n/10 KC1 vary 
from about 0*53 volt to 0'79 volt. Assuming that the p.d. 
at the electrocapillary maximum is most likely to be zero 
when the maximum is undepressed, it is probable that the 
p.d. Hg | ?i/10 KC1 does not exceed 0*53 volt. 
3. The polarizing E.M.F. required to produce the maximum 
surface-tension between mercury and a given electrolyte has 
been proved by Paschen to be equal, in many cases, to the 
E.M.F. of the corresponding dropping-electrode circuit. 
This relation is shown to be true in four particular cases in 
which each E.M.F. is equal to zero. It is also shown that 
