On Electric Phenomena. 21 



negative, and the hydrogen, which is secreted in the negative 

 plate, makes that positive ; a platina plate coated wdth oxygen 

 and one with hydrogen, are no longer homogeneous, but stand 

 in relation to one another like zinc and copper, they have 

 different electrical tension and form together a chain. 



That which takes place in the Yoltameter, must also 

 partly take place in the chain. In that, the current goes, as 

 we have already seen, from the zinc through the diluted sul- 

 phuric acid to the copper. It there decomposes the water, 

 the oxygen is parted from the zinc and the hydrogen from 

 the copper. Now the oxygen is innoxious ; as it has a great 

 anology to zinc, it forms in connexion with it a chemical 

 combination which is called oxyde of zinc, and this again 

 combines itself with the sulphuric acid to sulphuric oxyde of 

 zinc, or sulphate of zinc, which is dissoluble in water. The 

 oxygen, which is separated from the copper, occasions by its 

 strong positiveness a current from the copper to the zinc, 

 w^hich acts contrary to and weakens the original current. Thus 

 the chain contains in itself tbe cause of the diminution of its 

 strength. 



There are, however, means to obviate this cause. Da- 

 nielle an English Natural Philosopher, has specified a remedy, 

 which simply consists in removing the hydrogen, in the same 

 proportion as it rises. This is to be done, by surrounding 

 the copper with a fluid, which has a great chemical relation 

 to hydrogen. Such a fluid is a solution of sulphate of copper. 

 The hydrogen, as soon as it is formed, absorbs the oxygen 

 from the sulphate of copper and forms it into water, the cop- 

 per is parted from it and covers the plate at the pole with 

 an equal layer , as we have seen by the electro-metallurgy. 

 Thus the whole of the hydrogen is removed, and the copper 



(143) 



