LIQUID ELEMENTS OF THE VOLTAIC CIRCLE. 223 



binary theory of salts recognizes no essential difference between 

 the chloride, sulphatoxide, and oxide of a basyle, the oxide 

 being connected with the more highly saline compounds through 

 the sulphuret, and the chain of salt-radicals from iodine to 

 oxygen being continuous and unbroken. 



The facility of decomposition of different zincolytes appears 

 to depend more upon the high place of their salt-radical than 

 upon the nature of their other constituent. The iodides, for 

 instance, as iodide of potassium and hydriodic acid, are the 

 most easily decomposed of all salts, yielding to the polar influ- 

 ence of the sjngle circle. Then follow the chlorides, chloride 

 of lead, fused by heat, yielding to a very moderate power. 

 After these the salts of strong oxygen acids, such as sulphates 

 and nitrates either of strong bases, such as potash and soda, or 

 of weak bases, such as oxide of copper and water (the hydrated 

 acids are such salts). The carbonates and acetates, which have 

 much weaker salt-radicals, are still less easily decomposed, and 

 finally oxides are decomposed with great difficulty. Water itself 

 is polarized with such extreme difficulty, and decomposed when 

 alone to so minute a degree, even by a powerful battery, as to leave 

 its claim to be considered a zincolyte when in a state of purity 

 by no means certain. 



Widely as the more characteristic salt-radicals and basyles 

 differ, still the classes pass by imperceptible gradations into each 

 other, and form portions of one great circle. Mercury and the 

 more negative metals, although clearly basyles, appear at times 

 to assume the salt-radical relation to the highly positive metals ; 

 such a character is evinced in mercury, by the energy with which 

 it unites with sodium and potassium, and by its function in the 

 amalgamated zinc plate of the voltaic circle. So that the salt- 

 radical or basyle character of a body is not absolute, but always 

 relative to certain other bodies. 



The addition of a salt or acid, even in minute quantity, to 

 water in the cell of decomposition, causes the copious evolution 

 of oxygen and hydrogen gases at the zincoid and chloroid, and 

 is therefore often spoken of as facilitating, by its presence, the 

 decomposition of the water, in some way which cannot be ex- 

 plained. But the phenomena are unattended with difficulty on 

 the binary theory of saline bodies. When sulphate of soda 

 exists in the water of the decomposing cell, it is sulphatoxide of 

 sodium which is decomposed, SO 4 , the sulphate radical being 



