28 DESCRIPTION OF GALVANIC BATTERIES. 



The zinc in battery-cell lost 4J grains ; 



The copper in decomposition-cell lost 3^- grains. 

 These results show the importance of attending to the conditions 

 of the respective agents, and also, that distance in the decomposition- 

 cell offers greater resistance than distance in the battery-cell. 



Different Elements of Batteries. Although our observations have 



been made on zinc, copper, and dilute sulphuric acid in the battery- 

 cell, still these are not the only essential elements in a battery, as 

 almost any two metals with a liquid similarly arranged will produce 

 an electric current; but the current will vary according to the 

 nature of the metals employed, and the effects produced upon them 

 by the solution in which they are placed. If the exciting solution 

 has the power of acting upon both metals, as when zinc and copper 

 are immersed in dilute nitric acid, the current of electricity pro- 

 duced by the action of the acid upon the zinc will be neutralized to 

 an extent corresponding to the relative, action of the acid upon the 

 copper. To have any effective electrical power, it is necessary that 

 one of the metals employed be capable of combining easily with one 

 of the elements of the solution in which they are placed, and form- 

 ing a soluble salt, while the other does not ; and the power obtained 

 under proper circumstances has an intimate relation with these two 

 properties in contrast. The metal which undergoes solution is 

 termed the positive metal, the other the negative metal. Metals are 

 not considered to possess any intrinsic negative or positive principle ; 

 their relations in this respect are governed solely by the circum- 

 stances in which they may be placed. For instance, if we connect 

 a piece of copper and a piece of iron, and immerse them in acidu- 

 lated water, the iron is dissolved, and is positive in relation to the 

 copper; but if the same metals are immersed in a solution of 

 yellow hydro-sulphuret of potassium, the copper is dissolved, and 

 is positive relatively to the iron. Hence, to obtain a galvanic bat- 

 tery, the conditions are simply to provide two metals, and immerse 

 them in a solution capable of acting upon the one, and not upon the 

 other. The following table shows the order in which the common 

 metals stand to each other, in respect of their relative negative and 

 positive properties, when immersed in water acidulated with sulphu- 

 ric or muriatic acid the most intensely negative metal standing 

 highest, and the metal which acts most positively standing lowest : 



Platinum Copper 



Gold Lead 



Antimony Iron 



Silver Tin 



Nickel Cadmium 



Bismuth Zinc 



