1649 
Notwithstanding the use of a saturated solution of KCl as inter- 
mediary electrolyte and the employment of capillary connexions ot 
the latter with the hydrogen- and with the calomel-electrode, the 
readings in the zero-instrument, when dealing with little Cy, seemed 
to become either indistinct (owing to the great resistance), or 
inaccurate (presumably owing to diffusion). 
As our intention was mainly to ascertain whether the change in 
conductivity of the boric acid by the polyhydroxy-compounds was 
due to an increase of the concentration of the hydrogen ions, and 
as we, therefore, could be satisfied with an approximate value, we 
have provisionally contented ourselves with the results obtained. 
The calculation of the Cy from the conduetivity determinations 
took place from the relation: 
“— yy (An: + Ax) 
1 = gram equivalent per Litre. 
y == dissociation degree. 
CH = yn 1000 = enue zs : 
AH Hr 
Now, the sum of the migration constants (Aq: + Ax) of the com- 
plex boric acid compounds is not known; assuming it to agree with 
that found for acids with a not too small number of carbon atoms, 
we have put it at 380. For boric acid itself, this value is presumably 
too high. 
Example: Hydrogen-ion concentration of 0,5 mol. H,BO,. 
Insertion of the normal cell; reading on the scale = 511.3 
concentration chain; —,, „mn eS ASW) 
287 
+B) 
EMF = 
0 
oblo 
E of the calomel electrode = 0.337 se 
EMF of Ay (p = D|Cr- = 0:233' v. 
se : E 5 
Brome Te In Cy follows log Cy = — DOED TT 3,95 
Of = NAL Neat 
Caleulated from the specific conductivity x= 28.5 > 10 * 
1000 X 28.5 10-8 
Cz: =: 
< 380 
With boric acid these readings were not sharp, by way of control 
we have also determined the Cy of N/,, succinic acid and calcu- 
lated the H'-ion concentration from the known dissociation constant. 
= > 0,75 X 10%. 
