66 ELECTROLYSIS. 



We believe M. d'Arsonval's cells to be excellent, and par- 

 ticularly the first one, and should like to see their use become 

 popular. Perhaps it might be possible to replace the crown of 

 carbon pencils by the ordinary prismatic carbon wrapped in 

 cloth carbonised by the Caron process. The depolarising 

 surface would thus be increased, and the carbon part would 

 be stronger and necessitate less frequent cleanings. The rutilant 

 vapours which are emitted from every Bunsen cell can be sup- 

 pressed without altering the depolarising agent and without 

 complicating the cell by a system of a continuous flow of liquid. 

 This is effected by the very simple and efficacious means of 

 covering the surface of the porous cell with a layer, about 1 inch 

 thick, of ordinary colza oil. M. Rousse, Professor of Physics 

 to the Saint Etierme " lycee," discovered it, and M. Schreurs 

 experimented on it with success in M. Gramme's laboratory. 



DUCHEMIN CELL. This cell, which is used in M. Oudry's 

 works at Auteuil for the process of electro-gilding, is a Bunsen 

 cell in which the nitric acid has been replaced by a solution 

 of sesquichloride of iron. The sesquichloride of iron is reduced 

 by the hydrogen, yielding monochloride of iron and hydro- 

 chloric acid, which remains in solution. In this way the 

 polarisation is destroyed as in the Bunsen cell, and there is 

 no emission of gas. When the battery has been working for a 

 certain length of time, and the salts of iron have been brought 

 from a maximum to a minimum, it is sufficient in order to put 

 the cell in working order to send a flow of chlorine through the 

 solution of the salts of iron or to boil them with a few drops 

 of nitric acid. A certain economy is thus obtained, but the 

 manipulation of acid, however small, always acts prejudicially 

 against the propagation of any system of battery. 



LECLANCHE CELL. The Leclanche cell (Fig. 6) is com- 

 posed of a square glass vessel, contracted at its top, a positive 

 electrode consisting of a simple pencil of zinc, and a negative 

 electrode consisting of a central carbon plate and two agglo- 

 merate plates. The zinc pencil, the carbon, and the agglomerate 

 plates are kept together by means of indiarubber rings. The 

 liquid contained in the glass cell is a solution of sal-ammoniac. 



The agglomerate plates are composed of 40 parts of binoxide 



