1887.] Rate at which Electricity leaks through Liquids. 411 



so that JL — c(x— 1). 



The rate of leak = q/T, so that 



rate of leak _ c 



difference of potential at the end of the interval T ^ ' ~~ ' sa ^* 



Now if the conduction follows Ohm's law, 2 will be constant ; 

 hence Ohm's law will be obeyed if x be constant. The tables given 

 later on show how nearly constant x is. 



To test the accuracy of the law, we have — 



£2 hx Sx x 



2 x—1 x x—1 



so that a change of 1 per cent, in x will correspond to a change of 

 x—l/x per cent, in 2, and a deviation from Ohm's law to this extent. 



The liquids tried were benzene, olive oil, carbon bisulphide, and 

 paraffin oil. We could detect no deviation from Ohm's law for the 

 first three of these substances, though the difference of potential fell 

 from 500 scale divisions to 20. For paraffin oil, however, the con- 

 ductivity seemed slightly greater when the difference of potential was 

 large than when it was small. The departure from Ohm's law even 

 in this case was small. 



Quincke* has found that when the E.M.F. is comparable with that 

 which would cause a spark to pass through the liquid, Ohm's law 

 ceases to be even approximately obeyed. Thus, for carbon bisul- 

 phide, when the E.M.F. was 29-21 C.GLS. units, the current was 6*2 ; 

 when the E.M.F. was 47*74, the current was 36; showing that with 

 large electromotive forces the current increases much more rapidly 

 than the E.M.F. 



With the small electromotive forces which we used, the current, 

 however, is proportional to the E.M.F., showing that when the E.M.F. 

 is "com parable with that required to produce a spark through the liquid, 

 other methods of dissipating the energy of the electric field must 

 exist besides those which are active in conductors conveying a current 

 according to Ohm's law. 



We found that carbon bisulphide showed a phenomenon analogous 

 to electric absorption, the only case we know where this has been 

 observed in a liquid dielectric. 



The conductivity of all the liquids on which we experimented 

 increases as the temperature rises, so that in this respect they behave 

 like electrolytes. 



* ' Wiedemann, Annalen,' vol. 28, p. 529. 



