40 DESCRIPTION OF GALVANIC BATTERIES. 



four or five hours, during which it diminished in quantity gradually, 

 all of a sudden it seemed to recover its energy, giving a quantity and 

 power not much less than it gave in the first hour, and then declined 

 again rapidly, but occasionally renewing its vigour for short periods. 

 We have thought it probable that this reaction may be caused by 

 the formation of nitrate of ammonia in the rapid decomposition of 

 the nitric acid during the first action of the battery, which, as it 

 accumulates, may be reacted upon. 



The prevailing and permanent objection to the use of this ar- 

 rangement, not only for manufacturing purposes, but for many 

 experimental purposes, is this, that it emits nitrous fumes which 

 corrode every thing within their reach, and prove very disagreeable 

 to every person breathing them. For a smaU single pair of Grove's 

 battery it is very convenient to use a circular form, in which case a 

 little cylinder of wood, bored so that its sides be about ^th of an 

 inch thick, does well for a porous cell, and will last a long time. 



Smee's Battery. The ordinary defects in the common battery of 

 zinc and copper were much lessened by an ingenious contrivance of 

 Mr. ALFRED SMEE. This gentleman had observed that if the copper 

 plate of the battery be roughened, either by corrosive acids or by 

 rubbing the surface with sand paper, its action was made much more 

 efficient, the rough surface evolving the hydrogen much more freely. 

 Taking advantage, therefore, of this principle, he covered platinum 

 foil with a finely divided black powder of platinum, deposited by 

 electricity from a solution of that metal, and used this in place of the 

 copper in the ordinary battery. Instead of platinum foil, Mr. Smee 

 soon after adopted silver, which is much less expensive. The method 

 of preparing these plates is given by Mr. .Smee as follows : " The 

 silver to be prepared for this should be of a thickness sufficient to 

 carry the current of electricity, and should be roughened by brush- 

 ing it over with a little strong nitric acid, so that a frosted appearance 

 is obtained. It is then washed and placed in a vessel with dilute 

 sulphuric acid, to which a few drops of nitro-muriate of platinum 

 has been added. A porous tube is then placed into this vessel with 

 a few drops of dilute sulphuric acid ; into this tube a piece of zinc 

 is put, contact being made between the zinc and silver; the platinum 

 will in a few seconds be thrown down upon the silver as a black 

 metallic powder. The operation is now completed, and the platinized 

 silver ready for use." ! A simple method which obviates the use of 

 a battery is thus described : lay the silver between two pieces of 

 sand paper, and press it with a common smoothing iron, then pull 

 the silver out while under the pressure. The platinum solution is 

 made very hot, and the silver dipped in it for some time, which 

 effects the coating. 



1 Smee's Elements of Electro-Metallurgy, 2d edition, p. 24, 1843. 



