OF THE ATOMIC THEORY. 41 



gen may be which an acid contains, it is obvious 

 that the double of it must constitute an even 

 number, or a number divisible by 2, and conse- 

 quently a multiple of 2. 



As far then as the neutral salts are concerned, 

 Berzelius's law expresses nothing more, than that 

 the salifiable bases are mostly protoxides a pretty 

 remarkable fact, though JBerzelius himself was 

 not aware of it. Even in the neutral phosphates, 

 arseniates, and nitrates, and in the biphosphates, 

 binarseniates, and binitrates, the same law will 

 hold. It is only in the subsalts, and in those 

 salts that contain peroxides united to an acid, 

 that we can see whether this supposed law of Ber- 

 zelius be general or not. For example, sulphuric 

 acid contains 3 atoms of oxygen : now, it would 

 be a very remarkable circumstance indeed, if no 

 protoxide exist, of which 2 atoms are capable 

 of uniting with 1 atom of sulphuric acid. There 

 are but few subsalts known at present; yet when 

 I come to treat of the salts, I think I shall be 

 able to show examples of subsalts, which are in- 

 consistent with Berzelius's supposed law. Per- 

 oxide of iron is a compound of 1 atom of iron, 

 and H atom of oxygen; consequently, whether 

 it combine with 1 atom, 2 atoms, or 3 atoms, of 

 sulphuric acid, it is obvious that the oxygen of 

 the acid must be a multiple of the oxygen of the 

 base: For 3=1 -5 x < 2. But phosphoric acid is 

 a compound of 1 atom phosphorus, and 2 atoms 



