94 Mr. Napier on the unequal Decomposition of 'Electrolytes, 



will be equal to 90 ; and by increasing the action, either by 

 adding intensity or decreasing the resistance, so that it 

 amounts to 25 grains per hour, we decrease the tendency to 

 further action to 75, and so on, the one decreasing as the 

 other increases. Now, if this tendency for further action be- 

 tween the acid and zinc be the source of this feeble or unde- 

 composing current, and this the cause of an extra chemical 

 action at the positive over the negative electrode, then the 

 amount of this extra action at this locality will be greatest 

 with a w r eak battery, at least have some relation to the surface 

 of zinc exposed and the amount of actual chemical action 

 going on. That this is the case the following experiments 

 will show. To save repetition, I may state that when small 

 plates are mentioned the measures of the zinc are 2 by 2^ 

 inches; when large plates are named they measure 5 by 6 

 inches. 



1. With small plates, the electrodes being the same size as 

 plates, both placed in sulphate of copper with a very little 

 free acid. The current passing four hours, the results were 

 as under : — 



One pair negative gained 27 grs. Positive lost 30*5 grs. 

 Two pairs ... 44 ... ... 49 



Four pairs ... 58 ... ... 63 



Six pairs ... 70 ... ... 73 



Nine pairs ... 85 ... ... 87 



Taking these results in equivalent proportion, counting the 

 equivalent of copper 32, the extra action at positive will be — 



One pair 4'1 grains. 



Two pairs . . s . . . 3*6 ... 



Four pairs 2*7 ... 



Six pairs 1*3 ... 



Nine pairs ...... 0*7 ... 



The next experiment was with cyanide of potassium in the 

 proportion of 1 ounce to the pint of water. This was put into 

 one division of a decomposition cell, the other being charged 

 with sulphate of copper ; silver positive electrodes were used 

 in the cyanide solution. The battery used was of small plates, 

 the current passing two hours. 



One pair negative gained 14 grs. Positive lost 57 grs. 



Two pairs ... 14 ... ... 50 ... 



Four pairs ... 20 ... ... 70 ... 



Six pairs ... 21 ... ... 71 ... 



The equivalent of deposit being again taken, the proportions 

 of extra solution of positive stand thus; — 



