thing to be noticed now we are dealing with the chemistry of electricity, which is that the chemical power which destroys the colour is only due to the action on one side. I will pour some more of this sulphindigotic acid[1] into a flat dish and will then make a porous dyke of sand separating the two portions of fluid into two parts (fig. 50),
Fig. 50.
and now we shall be able to see whether 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 perceive any action none has taken place.
Here we have another instance of chemical
- ↑ Page 145. Sulphindigotic acid. A mixture of one part of indigo and fifteen parts of concentrated oil of vitriol. It is bleached on the side at which hydrogen gas is evolved in consequence of the liberated hydrogen withdrawing oxygen from the indigo, thereby forming a colourless deoxidised indigo. In making the experiment, only enough of the sulphindigotic acid must be added to give the water a decided blue colour.
