140 Galvanic Batteries. 



benefit is derived from the drying of the zinc plate unless it be 

 previously cleaned. From long and frequent use, I find that lead 

 is superior to copper for the negative plate. Immediately before 

 use, the surface of the lead which is to be opposed to the zinc 

 plate, should be well rubbed with coarse sand paper. It becomes 

 thus cleaned, and the numerous scratches made upon its surface, 

 serve as lodgments for the particles of copper deposited from the 

 solution of the sulphate. When the lead plate has been used a 

 short time, after such preparation, it receives a thick and ragged 

 coating of copper, aJffording an excellent conducting surface. 



The superior energy gained by drying the negative plate in 

 the amalgam battery, induced me to hope that a battery might 

 be constructed wherein the greatest amount of galvanic power 

 might be obtained with the least possible consumption of the 

 zinc. The experiment proves that galvanic^ is far from being 

 commensurate v/ith chemical action, and presents this singular 

 anomaly, that the galvanic 'power is greatest v)hen the chemical 

 action is the least. Considering the obvious mode of chemical 

 action in the battery, viz. the formation of the sulphate of zinc, 

 we have first in the series of actions the decomposition of the 

 water, the union of its oxygen with the zinc, and the simulta- 

 neous evolution of hydrogen as an indicator of the extent of this 

 action. But the escape of hydrogen, which mechanically im- 

 pedes the primal action of the battery, is protracted for a con- 

 siderable length of time when the plate is dried prior to its im- 

 mersion ; and during nearly the whole of this time, the electrical 

 action is at its maximum. Suppose now a number of copper 

 plates attached to the circumference of a wheel, and by the rev- 

 olution of the wheel these plates are presented to the zinc of 

 the amalgam in frequent succession. The last plate out of the 

 liquid would be the last to enter ; and if each plate could be 

 thoroughly dried in the course of its revolution, according to the 

 foregoing statements, the electrical action would be constantly 

 at its maximum, and the chemical action at its minimum. In- 

 deed, I see no reason why a continuous copper plate, revolving 

 slowly upon the circumference of the wheel, would not give 

 the same result, attended with the advantage of unceasing ac- 

 tion, provided one part of this plate could be d?ied before its im- 

 mersion. 



