Passage of Electricity through Liquids. 



269 



first column of tlie following Table and a multiplier of suitable 

 intensity with mirror-reading. The magnet, which was a steel 

 ring in a copper sheath with a plane silvered mirror, came to 

 rest in a few seconds. "From the ends of the resistance W, which 

 consisted of German-silver spirals, thin silver wires passed to the 

 pairs of quadrants of the electrometer. The values of the current- 

 intensity i and the values of w — v, measured by the deflections 

 of the electrometer, are measured in arbitrary divisions of the 

 instrument, and are the mean of two positiv^e and two negative 

 deflections. The calculation was made with the aid of equations 

 (2) and (4), under the assumption that the resistance 11 of the 

 circuit and of the conducting-wires amounted to 10 mercury 

 units. 



1 



w. 



Multiplier. 

 i. 



Electrometer. 

 u—v. 



Observed. 



Calculated. 



Observed. 



Calculated. 



CO 



1000 m.u. 



100 „ 



50 „ 



20 „ 







12-70 

 113-12 

 204-37 

 44228 







1314 

 120-6 

 221-1 

 442-28 



248-08 

 243-45 

 218-75 

 200-87 

 170-75 



245-7 

 225-6 

 206-7 

 165-4 



The deviations of the observed and calculated values are for 

 measurements with the multiplier and the electrometer of about 

 the same order, and may be explained by the difficulty of avoid- 

 ing alterations in the resistances on the passage of the current. 

 As resistance decreases in liquids with increase of temperature, 

 but increases in metals, the influences of the heating of the two 

 will compensate each other in the action on the multiplier ; but in 

 the action on the electrometer they will act in the same direction. 



The difficulty of keeping the resistance constant is far greater 

 in liquid conductors — for instance, solutions of cupric sulphate ; 

 for their resistance changes with the temperature to a far greater 

 extent than that of the metals. 



The electrical current of a Grove's pile of six cells was passed 

 through a reflectingmultipHer of suitable delicacy, and by means 

 of copper electrodes through an aqueous solution of cupric sul- 

 phate which filled a glass trough 440 millims. in length and 60 

 millims. in breadth to a height of 40 millims. The electrodes 

 were copper plates of the same section as the glass trough, and 

 were connected by thin silver wires with the pairs of quadrants 

 of the electrometer. Instead of the solution of sulphate of copper, 

 a series of German-silver spirals of equal resistance could, by 

 means of a rheostat, be interposed in the circuit, so that the thin 

 silver wires led to the ends of this metallic resistance. 



