IMPROVEMENTS IN THE VOLTAIC BATTERY. 459 



in force to common zinc, because of the lowering of its energy, which the mercury 

 might be supposed to occasion over the whole of its surface ; but this is not the 

 case. When the electric currents of two pairs of platina and zinc plates were opposed, 

 the difference being that one of the zincs was amalgamated and the other not, the 

 current from the amalgamated zinc was most powerful, although no gas was evolved 

 against it, and much was evolved at the surface of the unamalgamated metal. Again, 

 as Davy has shown*, if amalgamated and unamalgamated zinc be put in contact, 

 and dipped into dilute sulphuric acid, or other exciting fluids, the former is positive 

 to the latter, i. e. the current passes from the amalgamated zinc, through the fluid, 

 to the unprepared zinc. This he accounts for by supposing that " there is not any 

 inherent and specific property in each metal which gives it the electrical character^ 

 but that it depends upon its peculiar state — on that form of aggregation which fits it 

 for chemical change." 



1005. The superiority of the amalgamated zinc is not, however, due to any such 

 cause, but is a very simple consequence of the state of the fluid in contact with it ; 

 for as the unprepared zinc acts directly and alone upon the fluid, whilst that which 

 is amalgamated does not, the former (by the oxide it produces) quickly neutralizes 

 the acid in contact with its surface, so that the progress of oxidation is retarded, 

 whilst, at the surface of the amalgamated zinc, any oxide formed is instantly removed 

 by the free acid present, and the clean metallic surface is always ready to act with 

 full energy upon the water. Hence its superiority (1037.)» 



1006. The progress of improvement in the voltaic battery and its applications, is 

 evidently in the contrary direction at present to what it was a few years ago ; for in 

 place of increasing the number of plates, the strength of acid, and the extent alto- 

 gether of the instrument, the change is rather towards its first state of simplicity, but 

 with a far more intimate knowledge and application of the principles which govern 

 its force and action. Effects of decomposition can now be obtained with ten pairs of 

 plates (417.), which required five hundred or a thousand pairs for their production in 

 the first instance. The capability of decomposing fused chlorides, iodides, and other 

 compounds, according to the law before established (380. &c.), and the opportunity 

 of collecting certain of the products, without any loss, by the use of apparatus of the 

 nature of those already described (789. 814. &c.), render it probable that the voltaic 

 battery may become a useful and even economical manufacturing instrument ; for 

 theory evidently indicates that an equivalent of a rare substance may be obtained at 

 the expense of three or four equivalents of a very common body, namely, zinc : and 

 practice seems tlms far to justify the expectation. In this point of view I think it 

 very likely that plates of platina or silver may be used instead of plates of copper 

 with advantage, and that then the evil arising occasionally from solution of the cop- 

 per, and its precipitation on the zinc, (by which the electro-motive power of the zinc 

 is so much injured,) will be avoided (1047.)- 



* Philosophical Transactions, 1826, p. 405. 



