MICHIGAN ACADEMY OF SCIENCE. 
141 
SERIES II CELL NUMBER 2. 
Dilution of K Cl. 
Resistance in ohms. 
Dead point. 
II 
50.00 
+ 
10 
n 
389.17 
+ 
100 
T1 
3673.02 
+ 
1000 
n 
23 .196.50 
. 1 scale division 
10000 
Conductivity 
41,110.00 
8.5 scale divisions 
water 
cells were placed in a water bath at a constant temperature of 18° C. 
The “dead point” means that no movement of the galvanometer scale 
took place at one point, and that movement appeared if the contact: 
was changed one-tenth of a scale didivion on either side of the “dead 
point.” The test solutions used were solutions of K C L in the follow- 
ing dilution: N/10, N/100, N/IOOO, N/10000. In addition conductivity 
water having a specific conductance of 1.9 x 10-6 ohms was also tested. 
DISCUSSION. 
In this preliminary paper I have suggested some changes in the usual 
form of the apparatus commonly employed for determining the con- 
ductivity of electrolytes. These changes are in some respects similar 
to those made by Washburn & Miller whose paper came out before 
I had completed my work. In one respect I have introduced a more 
radical change in the apparatus since I make use of an alternating cur- 
rent galvanometer instead of the ordinary telephone. In regard to 
the use of the galvanometer this must be said : The zero indication 
(no deflection) will be largely dependent on the phase difference be- 
tween the two circuits. Now when the currents in both systems (swing- 
ing and fixed coils) are in quadrature no deflection will be produced 
in the galvanometer although there is considerable current present. 
A condition of this sort would lead to false readings on the bridge. In 
our work so far this condition has not arisen since we have alwavs 
obtained a deflection. 
A glance at the table will show that a high degree of precision lias 
been obtained and that only in the more dilute solutions does the bridge 
setting extend over more than 9 scale divisions. From a study of the 
paper published by the authors noted above we are assured that these 
results could be improved should we use the “extended” bridge wire, 
electrolytic cells with electrodes closer than 10 mm., and some form of 
resistances that are free from capacity and inductance. In regard to this 
latter item we expect to use in all our future work the new Curtiss 
Resistance Coils, which we are told are practically free from inductance 
and capacity and possess no temperature coefficient. The changes sug- 
gested in this paper give an easier and quicker method and one which 
at least attains a high degree of precision. 
Michigan Agricultural College, 
Experiment Station. 
