24 DESCRIPTION OF GALVANIC BATTERIES. 



The late Professor Daniell, disapproving of the terms cathode and 

 anode, substituted platinode for the negative, and zincode for the 

 positive, pole. We think these terms are better adapted for electro- 

 metallurgy, than cathode and anode, which have no direct reference 

 to ordinary conditions ; while zincode distinctly expresses the sub- 

 stance dissolved, and platinode the element not acted upon. 



Professor Graham adopts the terms zincous and chlorous poles, as 

 synonymous with zincode and platinode, or positive and negative. 



Although the terms positive, negative, and pole, may not be the 

 best, still, under all the conditions of electro -metallurgy, we deem 

 them as appropriate as any of the proposed substitutes, some of which 

 are based on supposed conditions which have not been proved, and 

 may be found incorrect. 



When we shall have occasion to use the two terms pole and elec- 

 trode, these will be used synonymously : positive and negative elec- 

 trode are synonymous with positive and negative pole. 



Electrolyte will be applied to a solution when undergoing decom- 

 position by the electric current passing through it. 



The positive electrode, or pole, is that metal in the electrolyte which 

 is being dissolved, or, if not capable of being dissolved, at which the 

 acid or solvent of the electrolyte is being liberated, as when sulphate 

 of copper forms the electrolyte, the sulphuric acid is liberated. The 

 negative electrode, or pole, is that metal or substance in the electrolyte 

 upon which the metal is being deposited by the influence of the 

 electric current, such as a medal upon which copper is being deposited 

 in an electrotype process. 



BATTERIES. 



Single Pair of Plates. If a piece of ordinary metallic zinc be put 

 into dilute sulphuric acid, it is speedily acted upon by the acid, and 

 hydrogen gas is at the same time evolved from its surface, having a 

 disagreeable smell arising from impurities contained in the zinc or 

 acid. If the zinc be taken out, and a little mercury be rubbed over 

 its surface, an amalgamation takes place between the two metals. If 

 the zinc thus amalgamated be again put into the dilute acid, there 

 is no action, for the mercury retains the zinc with sufficient force to 

 protect it from the acid. If a piece of copper be immersed along 

 with the zinc, and the two metals be made to touch each other, a 

 particular influence is induced among the three elements, zinc, cop- 

 per, and acid ; the acid again acts upon the zinc as if no mercury 

 was upon it, but the hydrogen is now seen to escape from the surface 

 of the copper : this action will go on as long as the two metals are 

 kept in contact. Or if, instead of causing the two metals to touch, 



