charged xmth a Solution of Sulphate of Copper. 24-5 



ing set at liberty ; and as the hydrogen assumes the gaseous 

 form, it annuls or carries off a large portion of the electri- 

 city*. 



If sulphate of copper be used in charging the battery in- 

 stead of acid, oxygen is supplied to the zinc by the oxide of 

 copper; no evolution of gas, therefore, takes placet; and the 

 action is thus rendered continuous, the effect being fully equal 

 to that momentarily produced by immersion in acids. The 

 fusion of metallic points of very large dimensions, the decom- 

 position of fixed alkalis, &c. &c., cited in my former commu- 

 nication as the effects of a voltaic battery of 100 pairs on 

 Cruickshanks's construction, cannot be produced by the same 

 battery when charged with acid, the momentary power being 

 exhausted before the battery can possibly be brought into ac- 

 tion |. 



The following is an experiment to ascertain the effect on the 

 battery produced by the deposition of copper on the zinc plate. 

 Fig. 10 represents one of the zinc plates of the battery : round 

 it at («) are placed four copper wires one tenth of an inch in 

 diameter; these are each attached to the plates by a drop of 

 solder. Fig.l I shows the zinc plate surrounded by the copper as 

 in Wollaston's plan : the battery consists of twelve such series. 

 It is clear that there are four small local currents in each cell ; 

 yet the power of the main current is increased, and not dimi- 

 nished as I conceived it would have been. From the proxi- 

 mity of the copper wires to the zinc plate, there is no deposi- 

 tion of copper on the zinc plate; it adheres to the copper wires 

 so firmly that it is exceedingly difficult to remove. 



I find that amalgamating the zinc greatly increases the 

 power of the battery, and prevents the strong adherence of the 

 copper to the zinc plates, which are therefore cleaned with 

 facility §. I have a battery of 30 pairs of four-inch plates 



* A similar effect takes place in the formation of steam, which causes the 

 gold leaves of an electrometer to diverge with negative electricity. 



Professor Faraday has shown that a voltaic current ceases to affect a 

 magnetic needle if employed in the decomposition of a solution of iodide of 

 potassium : hydrogen is given off in this case. Again, if a battery be euj- 

 ployed in decomposing a solution of a metallic salt, an atom of it will be 

 decomposed for the solution of every atom of zinc ; but this does not de- 

 stroy the current, for an atom of water is at the same time resolved into 

 its elements. 



f The exceedingly small quantity produced by the local action cannot 

 be taken into account. 



X This fact I am ready to prove by actual experiment to any scientific 

 gentleman who will do me the favour to call for that purpose. 



§ The zinc plates are anralgamated by rubbing them with dilute nitric 

 acid and mercury ; the mercury is allowed to be absorbed by the zinc plate, 

 and the operation muat then be repeated, which is a requisite condition. 



