﻿272 Dr. Paalzow on the Galvanic Resistance of Liquids. 



The fundamental idea which regulated the construction of the 

 apparatus was the following. In order to limit a defined quan- 

 tity of the liquid investigated, a siphon tube had to be filled 

 with it, and this connected with the electrodes and the conduct- 

 ing liquids, so that the values for the resistance of the liquid in 

 the siphon tube were as great as possible in comparison with 

 the resistance of the conducting liquids and the inequality and 

 polarization of the electrodes. But to exclude these latter un- 

 avoidable magnitudes in each individual experiment, a second 

 siphon tube had to be connected with the electrodes in the same 

 manner, the dimensions of this second tube being either consi- 

 derably greater or smaller than those of the first tube. The re- 

 sistance of the liquid alone could be determined from the differ- 

 ence of the two numerical values, provided that in the time which 

 elapsed between two observations no alteration had occurred in 

 the electrodes or in the conducting liquids. The resistances had 

 to be referred to mercury as unit. 



Two wide glass vessels were filled with a concentrated solu- 

 tion of sulphate of zinc, and as large electrodes as possible of 

 amalgamated zinc placed in them. Over these electrodes porous 

 cells were placed, which were connected by a siphon tube. Both 

 cells and siphon tube were filled with the liquid to be inves- 

 tigated. 



The zinc electrodes of the apparatus were connected with the 

 conducting-wire of one branch of a Wheatstone's bridge, while 

 in the other bridge a normal resistance-coil of 0*1 to 50000 

 Siemens units was introduced. Such a proportion of this re- 

 sistance was introduced that the terminal of the wire of the 

 bridge was as near the middle as possible. 



When the observation for the first siphon tube was ended, 

 the first siphon was replaced by a second, and, for control, fre- 

 quently by a third. Beginning with the largest, the second was 

 filled with the liquid contained in the first, the third with that 

 in the second; so that almost exactly the same quantity of 

 liquid was retained. After inserting suitable resistances, the 

 numbers were read off on the measuring-line. 



By preliminary experiments the resistance of the mercury was 

 measured which filled the siphon tubes, and the difference of 

 the mercurial resistances of every two tubes calculated once 

 for all. 



In order then to obtain the resistance of the liquid referred 

 to mercury as a unit, the difference of the resistance of the 

 liquid had only to be divided by the difference of the mercury- 

 resistance of every two siphon tubes. With three siphon 

 tubes, therefore, the three possible quotients must give the 

 same numbers. But even with two siphon tubes a simple control 



