xiv THE ATOMIC THEORY 295 



Dalton's Berzelius's 



Molecules. Symbol. Symbol. 



Nitric oxide . . . O O + N 



Nitrous oxide . . , O O + 2N 



Nitrogen peroxide . . OO 2 + N 



Carbonic oxide . . . O C + O 



Carbonic anhydride . . O C + 2 



Berzelius's atomic symbols (1819) Dalton's system of 

 symbols was much improved by Berzelius, who, in his Essay 

 On the Theory of Chemical Proportions, published in 

 Paris in 1819, suggested that "Chemical symbols should be 

 letters of the alphabet, in order to be easily drawn and 

 printed without disfiguring the text " ; he therefore " chose 

 for this purpose the initial letter of the Latin name of each 

 element ' ?1 (loc. tit., p. in). Since many elements had the 

 same initial he proposed to use single letters to represent the 

 chief non-metallic elements, and to add a second letter to 

 distinguish the metals or other non-metals having the same 

 initial. As examples he gives : 



S = Sulphur. C =Carbonicum (carbon.) 



Si =Silicium (silicon). Co = Cobaltum (cobalt). 



Sb = Stibium (antimony). Cu = Cuprum (copper). 

 Sn Stannum (tin). 



O =Oxygenium (oxygen). 

 Os = Osmium. 



Compounds were distinguished by adding together the 

 symbols of the constituent elements, e.g. the two oxides of 

 copper were written Cu + O and Cu + 26. Berzelius 

 abbreviated his symbols by writing these two compounds 

 as Cu and Cu, the dots representing atoms of oxygen. In 

 the systems as used in the present day the two formulae 



1 In a Swedish pamphlet published in 1814 Berzelius used initial 

 letters to represent the oxides of the chief mineral-forming elements. 



