CHEMICAL ACTION OF THE BATTEEY. 145 



thing to be noticed now we are dealing with the 

 chemistry of electricity, which is that the chemi- 

 cal power which destroys the colour is only due to 

 the action on one side. I will pour some more 

 of this sulphindigotic acid ( 23 ) into a flat dish 

 and will then make a porous dyke of sand sepa- 

 rating the two portions of fluid into two parts 

 (fig. 50), and now we shall beable to see whether 



Fig. 50. 



there is any difference in the two ends of the 

 battery, and which it is that possess this peculiar 

 action. You see it is the one on my right 

 hand which has the power of destroying the blue, 

 for the portion on that side is thoroughly 

 bleached, while nothing has apparently occurred 

 on the other side. I say apparently, for you 

 must not imagine, that because you cannot per- 

 ceive any action none has taken place. 



Here we have another instance of chemical 



