i:i.i.rn:ni.YTic LAW.-. Ill 



riivuit. This law, which is expressed as regards a zinc cell 

 used as a generator of current, is general, and is verified with 

 any other cell. It is a consequence of the second law which 

 demonstrates that the current acts in the electrolytes in the 

 s.i mo manner as in the cell, and that the chemical work of a 

 current is the same in the whole of its course. 



All the foregoing can be verified by means of simple de- 

 compositions, provided a secondary action does not come into 

 play ; but, in practice, there often occur some secondary phe- 

 nomena due to the chemical action of the constituents which 

 are carried to the electrodes, owing either to the decomposition 

 of the water of the bath by the metal in its natural state, or to 

 the anode being attacked by the liberated acid and oxygen. 



The effects of the electro-chemical decomposition in definite 

 proportions, vary according to the temperature and the nature 

 of the dissolving electrodes, and of the dissolved compound. 



If we fail to verify Faraday's law, it would be owing to 

 neglecting to take into account one or many of the causes 

 which may influence the result of electrolysis. 



ELECTRO-CHEMICAL EQUIVALENTS. The electro-chemical 

 equivalents are the weights of various electrolytes decomposed 

 for each unit of electricity. The electro-chemical equivalents 

 are proportional to their ordinary chemical equivalents. 



There is no difficulty in defining the electro-chemical equiva- 

 lents of analogous chemical compounds; but if in the same 

 circuit the electrolysis of water is produced together with that 

 of a series of neutral sulphates of protoxide, for example, the 

 electro-chemical equivalent of each metal is the weight which 

 is deposited for the liberating of 0*00001036 gramme of 

 hydrogen. If the compound substances have not the same 

 formula, one may experience some difficulty with two neutral 

 sulphates, one of protoxide, the other of sesquioxide of iron 

 decomposed by the same current ; it may be asked if the same 

 weight of iron or of oxygen will be liberated in the two baths. 

 M. Ed. Becquerel has demonstrated that it is the metalloid 

 which rules the case. Consequently, the weights of iron, in the 

 two electrolytes, will be in the ratio of 3 to 2. The same rule 

 applies to the salts of other acids, the chlorides, sulphides, &c.* 

 * ' Le9on8 ant I'clectricite et le magndtisme,' par E. Mascart et Joubert. 



c2 



