Inductive Capacity of Electrolytes. 201 



Summary. 



V. (a) The expression for the force between two electrodes 

 having a homogeneous medium between them, thus forming a 

 condenser, is of the form 



F=AKV 2 . 



For a given liquid and given electrodes at a constant distance 

 F is proportional to V 2 . This is found to hold for electro- 

 lytes as well as dielectrics through the wide range of poten- 

 tials employed. 



(b) When the potentials and medium are constant and the 

 distance between the electrodes varied, the value of F in the 

 above equation varies in a manner sensibly independent of 

 the nature of the medium, depending only on the capacity of 

 the condenser. 



(c) When the speed of the commutator changes, the force 

 is but slightly altered, unless the electrolyte is a fairly good 

 conductor. In the latter case the force is diminished as the 

 speed is reduced, owing to polarization. There is a small 

 change in the force with turpentine due to variation of speed, 

 although none in the case of air. With turpentine, as with 

 pure water and alcohol, the change is very small, the force 

 being greater in every case with higher speeds. 



(d) When the conductivity of distilled water is increased 

 by adding hydrant water or minute quantities of acid or 

 copper sulphate, the force is not greatly altered, although the 

 current increases many times. The force, however, decreases, 

 which is believed to be due to polarization. Were the latter 

 wholly eliminated, the force would probably remain unaltered ; 

 at most it could differ but little. 



(e) When the temperature rises, other circumstances re- 

 maining unaltered, the conductivity increases while the force 

 decreases, the rate being constant or nearly so within the 

 range of experiment. This decrease in the force, however, 

 cannot be accounted for by polarization, for the increase of 

 conductivity is not sufficient to make an appreciable difference 

 in polarization effects. This is further proved by the fact that 

 the force is immediately increased by a small decrease in the 

 temperature, the curve returning upon itself, while if it were 

 a case of polarization, the curve would more resemble the 

 hysteresis-curve of magnetization. 



VI. The almost complete agreement between the behaviour 

 of the given electrolytes and that of dielectrics seems to show 

 that the force acting on the needle is wholly independent of 

 the quantity of current and of the conductivity of the medium, 

 and it is difficult to conceive how the force and conductivity 



