2 90 On Electrolysis and the Passage ofElectricity through Liquids, 



and closed at both ends with corks. Two amalgamated circular 

 cadmium plates were soldered to copper wires which passed air- 

 tight through the corks to the outside. In the axis of the tube 

 a hollow glass thread of 0*7 millim. outer and 0'3 inner dia- 

 meter was fixed_, which was filled with mercury, and communi- 

 cated with the outside by means of suitable openings in the 

 cadmium plates and corks. By a small glass tube in one of the 

 corks the apparatus could be filled with liquid without taking it 

 to pieces. 



The electrical current passed from one cadmium electrode, 

 through a column of liquid 200 millims. long, to the other elec- 

 trode, and then immediately back in the axis of the tube through 

 the thread of mercury. Such a conductor could exercise no de- 

 flecting force on a magnetic needle when the intensity of the 

 current was the same in the electrolytes and in the metal wire 

 in the axis. The tube thus arranged was placed on a small 

 slide, parallel to the magnetic meridian inclined to the horizon 

 at an angle of 45° ; and, together with the slide, its centre was 

 placed as near as possible to a magnetized steel mirror, which 

 was suspended in a thick copper sheath to a cocoon thread, and 

 its oscillation regulated to 19" by a correcting bar. When the 

 electrical current of a Grovels battery of 20 elements traversed 

 only the liquid in the glass tube, the magnetic mirror seen 

 through a telescope was deflected about 330 divisions of the 

 scale ; when the current traversed the liquid column and the 

 mercury thread in opposite directions simultaneously, then the 

 deflection was from 3 to 5 divisions in the direction of the elec- 

 trical current in the thread of mercury. 



It may be observed that, in consequence of the great resist- 

 ance of the liquid, the current was excessively weak, being about 

 •0000351 of an electromagnetic unit. 



"When instead of the alcoholic solution of iodide of cadmium 

 the same apparatus was filled with a concentrated aqueous solu- 

 tion of sulphate of copper (specific gravity = 1*166) and the 

 current of a Grovels element passed through it, there followed, 

 since the resistance was now diminished nearly to one sixteenth 

 of the resistance with the solution of iodide of cadmium, a de- 

 flection of 260 divisions. When the current traversed the solu- 

 tion of sulphate of copper and the thread of mercury in opposite 

 directions simultaneously, then the current in the latter slightly 

 preponderated and produced a deflection of 5 divisions. 



This slight deflection is accounted for by the fact that the 

 glass thread containiog the mercury was not fixed exactly in the 

 axis of the tube ; and hence it follows that the intensities of the 

 current in metals and in electrolytes are equal, within 1 per cent. 

 at any rate. Kohlrausch with dilute sulphuric acid and aqueous 



