Structure of Simpler Organic Compounds. 49 



taining a single carbon atom united with these elements 

 having such formulae as the following : 



(1) CH 3 C1 (2) CH 2 C1 2 (3) CHC1 3 (4) CC1 4 

 (5) C0 2 (6) H 2 CO (7) HCN 



Such substances are in fact known, and are designated 

 (1) monochlorme thane or methyl chloride, (2) dichlor- 

 methane, (3) trichlormethane or chloroform, (4) tetrachlor- 

 me thane or carbon tetrachloride, (5) carbon dioxide, (6) 

 formaldehyde, (7) hydrogen cyanide or prussic acid. In 

 the first four compounds carbon is united to four uni- 

 valent atoms (which need not all be of the same element) ; 

 in the fifth, to two bivalent elements ; in the sixth, to 

 two univalent elements and one divalent element ; and in 

 the seventh, to one tervalent element and one univalent 

 element. In all cases the sum of the valencies of the 

 elements united with carbon is four, and the valencies 

 themselves are deduced from the formulae of simple com- 

 pounds of the various elements with hydrogen. 



These conceptions are usually indicated by a graphical 

 method. A single line is used to indicate each unit of 

 valency. Methane would thus be represented by the 

 formula TT 



H C H 



H 



Carbon dioxide by the formula 



0=0=0 



(the bivalent element oxygen having its valency represented 

 by two lines), and hydrogen cyanide by the formula 



H C = N 

 In the above three cases, the hydrogen, oxygen, and 



(1..997) 4 



