RESISTANCE OF ELECTROLYTES. 25 
terms of known resistances. If the sections of the tubes are the same, and the lengths 
known, the specific resistance of the electrolyte can be at once determined. If not, the 
cells may be filled with a liquid of known specific resistance, and the resistances of all 
other liquids determined by reference to it. 
This result seems to shew that the use of alternating currents is without profit. For 
it is as true of continuous as of alternating currents. I have thought it well to use the 
latter, however, because of the difficulty of cutting electrodes of exactly the same area, 
and of getting coils of wire of exactly the same resistance. There must always be slight 
differences, and consequently slight polarization, and hence it is advisable to reduce this 
slight polarization by the use of alternating currents to so small an amount that the 
difference in its values in the two cells may not be such as to affect the galvanometer. 
The resistances R, and R; of the cells E and E> may include not only the resistance of 
the electrolyte in the cells, but also a special resistance at the surface of the electrode. 
This special resistance which has been called transition resistance, may or may not exist. 
-No experiments have yet been made which are conclusive on this point. Even if it does, 
however, the method which I have described eliminates it. For as currents of the same 
strength are passed through the same electrolytes between equal electrodes, the transition 
resistance in both.cells must be the same. Hence, ifm, rare the resistances of the electro- 
lyte in E, and E,, and if pis the transition resistance, 
R, = 1, + p, and R, = r, + p; 
and, therefore, 
R, — Rk, = n—n, 
whence 
Y, — Lo = R, 3 KR = Re 
The use of Wheatstone’s bridge involves the passage of currents through the electro- 
lyte before the measurement of resistance can be made, and the passage of such currents 
must be attended by a change in its constitution. We have here, therefore, a source of 
error. The above method, however, reduces this error to an exceedingly small quantity. 
For the galvanoscope is so sensitive that the necessary currents may be very weak, and 
need have but very short duration, amounting on the whole to perhaps a few seconds. 
The decomposition effected by such quantities of ,electricity can have no appreciable effect 
on the constitution of the electrolyte. 
The most of the experiments by which the above method of measurement was 
developed, were made. in Prof. G. Wiedemann’s Physical Laboratory in the University of 
Leipzig. I hope before long to lay before the Society some determinations of the resistances 
of electrolytes made by means of it. 
Ihave great pleasure in taking this opportunity of expressing my indebtedness to 
Prof. Wiedemann for his kindness in placing the best of apparatus at my disposal, and for 
the valuable advice which he was always ready to give me during the whole course of 
my experiments. 
Sec. III., 1882. 4. 
