244 Mr. De la Rue on the Effects of a Voltaic Batter?/ 



of two inches breadtli, of plates (the size which we have taken 

 above as an example), may be contained in a trough eight 

 inches in length, and will evolve, when its terminal wires are 

 soldered to a Faraday's volta-electrometer, six or seven cubic 

 inches of the mixed gases in three or four minutes, with a 

 charge of half an ounce of sulphuric acid and half an ounce 

 of nitric acid, in twenty-four ounces of water, (all by fluid mea- 

 sure,) and is therefore amply sufficient to demonstrate the de- 

 composition of water on a considerable scale. 



It is proper to use the thickest sheet zinc which can be 

 had, in the construction of the plates, although the thinnest 

 sheet copper will suffice, from its being so well supported. 

 When the zinc plates are worn out, the cross-bars may easily 

 be pulled out of the solid ends, and the elements of the bat- 

 tery separated. New zinc plates being soldered to the old 

 coppers, the whole may again be quickly rearranged in the 

 old frame. 



Glasgow, Jan. 4, 1837. 



XLIX. 0?i the Effects of a Voltaic Battery charged with Solu- 

 tion of Sulphate ofCopjwr. By Mr, Warren De la Rue. 



[With Figures : Plate II.] 

 To the Editors of the Philosophical Magazine and Journal, 

 Gentlemen, 



IN answer to your query (vol. ix. p. 484<,) as to the relative 

 effects of batteries charged with sulphate of copper or with 

 acids, I beg to submit to your attention the following facts 

 and deductions. 



It is well known that in connecting the poles of a battery 

 with a definite length of wire, the wire will become ignited, 

 and continue so for an exceedingly short space of time after 

 immersion in an acid ; and if the battery be immersed without 

 connecting the poles and allowed to remain for a few minutes, 

 and the connection be then made, — with the same length of 

 the same wire, — no ignition whatever is produced*. As in 

 this latter case no zinc can have been deposited on the copper 

 plate, prior to the connection of the poles, it follows that this 

 decrease of power must result from some other cause. At the 

 moment of immersion in dilute acid, say sulphuric, the elec- 

 tricity is produced by the combination of the acid with that 

 portion of oxide which is in perfect contact with the zinc 

 plate: when this thin coating of oxide is removed, the zinc 

 plate is then oxidized at the expense of water, hydrogen be- 



• A battery regains its former power by exposing the plates to the 

 action of the atmosphere. 



