1648 
the liquid of which this concentration was measured, was selected 
as small as possible. 
Mee 
Ed oom L 
Seale 
The following sketch gives a survey of the arrangement of the 
determination. 
RT DH. 
The EMF. of this chain B, = —~ In EB Ben 
If the pressure of the hydrogen is kept at one atmosphere then 
V pH, = WE 
The EMF of this chain #, is compared with that of a standard 
normal cell Z,; if the readings on the scale are a, and a,, then 
bij B, ha: E 
From the difference in potential 7, (p =1) Cp, which thus in regard to 
7” 
the normal hydrogen electrode = ins In Cy, the known potential 
difference of the calomel electrode (also calculated with respect to the 
normal hydrogen electrode) = 337 millivolt and the found electro- 
motoric force of the concentration chain, the concentration of the 
HT can be calculated. 
The normal cell employed was compared with a standard instru- 
ment and had an EMF of 1.0177 at 18°. 
The hydrogen used for determining the potential difference //,/ Cy was 
very carefully purified, the platinum wire was freshly platinised and 
was only superficially plunged into the electrolyte. 
This part of the concentration chain was placed in a thermostat 
at 25°, because the Cy had to be compared with that calculated 
from the conductivity measurements which were carried out at 25°. 
As the calculations in regard to the norma! hydrogen electrode 
relate to 18° and as this is sensitive to the temperature an error is 
made of a few millivolts; this, however, is within experimental errors. 
