BATTERIES. 65 



BuDsen battery. He has preserved the general arrangement 

 of the latter. 



Instead of a prism of carbon, M. d'Arsonval introduces, in 

 the porous jar, a bundle of cylindrical carbon pencils one centi- 

 metre in diameter. These pencils are united together by dipping 

 one end of the bundle for a few minutes in boiling paraffin ; 

 when cold, this end is coated with a galvanic deposit of copper, 

 and finally covered with a ring of printing-type metal cast 

 upon it. The depolarising surface is thereby greatly increased 

 at the same time that the internal resistance of the cell is 

 reduced. 



The zinc preserves its form and its position, but the liquid in 

 which it is immersed is modified. Instead of dilute sulphuric 

 acid, it is a mixture composed of hydrochloric and sulphuric 

 acids, the volume of both being in the proportion of ^V The 

 sulphuric acid is not, in this case, obtained from sulphur, as is 

 the case with the ordinary Bunsen cell, but from pyrites; to 

 purify it, one-sixth of an ounce of colza oil is poured into the 

 sulphuric acid for each quart of the latter. The oil is decom- 

 posed, sulphoglyceric acid is formed, and the impurities are 

 precipitated in a state of insoluble soaps. 



The presence of fat acids facilitates the amalgamation, and 

 the zinc is scarcely attacked when the circuit is opened. 



In order to prevent the zinc being attacked by the filtration 

 of the nitric acid through the porous jar, M. d'Arsonval mixes a 

 small quantity of sulphate of soda in the acidulated water. 



The depolarising solution in which the bundles of carbons 

 are immersed is of the following composition : 



Nitric acid 1 volume. 



Hydrochloric acid 1 



Acidulated water per JL of HO, S0 8 . . . . 2 volumes. 



Thus prepared, one cell 8 inches high can easily give 

 25 amperes per second with an electromotive force of 2 volts, 

 which corresponds to an electrical energy of 5 kilogrammetres. 



In order to avoid any smell, M. d'Arsonval combines a cell 

 with broken carbon and a continuous flow in the porous cell of 

 a liquid composed of equal volumes of water saturated when 

 cold with bichromate of potash and hydrochloric acid. 



