534 Proceedings of Royal Society of Edinburgh. 
involved. It could only be ascribed to an increase of polarisa- 
tion, similar to that observed in the electrolysis of mixed 
salts. 
By leaving the ammeter and voltmeter continuously in circuit 
during several experiments, the progress of the change was studied 
more fully. It was found to take place in a somewhat peculiar 
manner. The rise of potential began very gradually, but before 
long the needle sprang back to its former position; this was 
followed by another slow, steady rise, again followed by a sudden 
lapse. These changes continued for some time, the increase 
becoming more and more marked, and the lapses gradually less and 
less frequent, and finally the instrument remained steady at about 
0-4-0-5 volt above the former level; prolonged electrolysis had 
very little further effect, if any. 
In order to test the value of this effect as an indicator in 
quantitative determinations, a number of experiments were carried 
out with varying quantities of nickel, employing the methods 
already indicated, but stopping the electrolysis as soon as the volt- 
meter indicated that the potential had risen to the higher level, 
instead of waiting the standard time of 4 hours, as was done 
previously. In every case the results were quite satisfactory, and 
were no lower than those obtained in duplicate determinations in 
which electrolysis was continued an hour or two longer. A 
selection of typical results is given below. 
Weight of Weight of Per- m- 
Salt. Deposit. centage. 
h.m. 
I. 0*9075 0*1342 14*78 0.0 
Volt. Amp. Temp. 
3-15 0-62 14 
3-2 -63 22 
3-2 -64 24 
3 2 -63 25 
3-35 *63 
1.0 
1.45 
2.0 
2.15 
2.30 
2.40 
2.50 
3.0 
3-35 *63 
3*35 *63 
3*5 -62 
3-6 *61 25 
II. 0-4378 0-0646 14*76 0.0 3’3 0*62 12 
1.45 3-35 *62 22 
2.0 3*4 -61 
2.15 3-45 -60 
2.30 3*5 -60 
2.45 3-5 -60 
3.0 3-7 -59 22 
