Measure of the relative Tension of Electric Currents. 3^1 

 Table H. 



Exp. 



Acid. 



Sulphuric. 



Nitric. 



Sulp. 



Nitr. 



Sulp. 



Nitr. 



Quantity in drachms. 



1 

 1 



2 



Quantity. 



23 

 53 



72 



.94 



178 



190 



Tension. 



.5652 

 •5094 

 •3888 

 •3510 

 •2360 

 •2026 



Solution of SULPHATE of COPPER was next experimented 

 with. 



Tliese measures were procured with difficulty, owing to the 

 flocculent deposit which settled on the zinc, more rapidly as 

 the solution was made stronger. 



In the general discussion of the measures, given by tables 

 E, F, G, H, I, we still see the operation of the same general 

 law, that the tension rapidly diminishes as the acid is added, 

 and that when the same quantity of electricity developed from 

 the same amount of surface by these different acids is pre- 

 sented to the secondary wire, the quantities that can pass that 

 wire are very different ; and on making use of these different 

 agents it would appear that they can give rise to currents 

 from the same metalline surface, equal in point of quantity, but 

 differing greatly in point of tension, in the followdng order, 

 beginning with the most powerful : 



Sulphate of copper, 



Nitric acid, 



Nitrosulphuric acid, 



Muriatic acid. 



Sulphuric acid. 

 Of these bodies the muriatic acid acts probably in the way 

 that Dr. Faraday has pointed out, but the immediate cause of 

 the rise of tension in the others, is to be traced to the circum- 

 stance, that they furnish oxygen to the nascent hydrogen ; and 

 if the tension of the ordinai-y current is made to depend on 

 the tendency of the zinc and oxygen to unite, it is reasonable to 

 suppose that that tension will increase if a new affinity be in- 



