772 
solution of iodide, of 0.8°/, for bromide, and of 20°/, for chloride. 
That the error for chloride is so exceedingly large, larger than 
is necessary, is owing to Reepy’s method of working. He wanted, 
namely, to precipitate halogen, till no more than 0.1 mgr. was left 
in 200 em? of the solution. For this purpose he calculated the potential 
which a silver electrode covered with AgCl presents in a solution 
of 0.1 mgr. per 200 em”. and then carried out the electrolysis for 
this constant anode potential. Hence the halogen concentration at the 
anode was kept constant, and ci, in equation (1) had the value 
0.000014 for Cl, the value 0.000007 for Br, and 0.000003 for I. 
The ratio of the quantity of silver halide, which precipitates in 
the liquid to that which precipitates on the anode is according to (1) 
DE 
IAD ee ap 
As now Laga is about 1.4 10-10, Lager 9 X 10-B, and 
d 
Beer OTB, 5 becomes 0.7 for chlorine, 0.01 for bromine, and 
( 
1 
0.001 for iodine. 
The value calculated here for silver chloride is much greater than 
that of Reepy, which can be explained by this that the values of 
Ciq used are not very accurate. When c;, differs little from WL, a 
d, . 
small error in cy, gives a great change in the value ~. For AgBr 
1 
and Agl, where cy, is much smaller than WL, an error in ci, brings 
d, 
a, 
As for 1°/, bromine that precipitates in the liquid as AgBr, about 
1*/, times the amount of silver of the anode dissolves, the total 
error calculated for the bromine determination is about 2.5 °/,. In 
the iodine determination it amounts to about 0.2 °/,. It appears, 
therefore, that in these latter determinations the calculated error 
corresponds in order of magnitude with the deficit in Rexpy’s deter- 
minations. 
about only a small absolute change in 
As was already observed above the determination of chlorine as 
silver chloride can be made more accurate than was done by Rexpy. 
For this purpose the concentration of the chlorine ions at the anode 
must be kept at a higher value, e.g. 1 mgr. instead of 0.1 mgr. 
per 200 em’. 
Further Reepy has determined some current potential lines, as they 
have been drawn in fig. 2 of the first paper, among other things 
for KI (fig. 3 p. 286 Rerpy). A quantitative comparison of the theo- 
