MOLECULAR ARCHITECTURE 



439 



the arrangement of the multivalent atoms forming the 

 skeleton, and the method of attachment of the other atoms 

 to this skeleton. 



We also owe to Kekule a revival of the GRAPHIC 

 FORMULA, which Dalton had used to indicate the number 

 and the nature of the atoms (p. 295), but which Kekule 

 proposed to use in order to show also the way in which the 

 atoms were linked together. The univalent atoms were 

 represented by circles, the bivalent atoms by a dumb-bell 

 figure occupying the width of two circles, and so on. In 

 all the simpler compounds, the atoms were arranged in two 

 equal horizontal rows, and every point of contact between 

 the two rows indicated a linkage between two atoms. A 

 number of Kekule's graphic formulae (Lehrbuch, 1861, I. 

 1 60, 162, 164, footnotes) are shown below, together with 



Simple Inorganic 

 Compounds. 



Hydrogen chloride 



Kekule's 

 graphic 

 formulae. 



Modern Modern 



structural graphic 



formulae. formulae. 



HC1 



H-C1 



or V 7S< 

 C1-SO 2 -C1 C1-O-S-O-C1 



or ^S^ 

 HO-SO 2 -OH H-0-O-S-O-OH 



ON-O-OH O = N-O-OH 

 or NO 2 -OH or *N-OH 



1 In these cases the structure given by Kekule differs from that wtdch 

 is commonly accepted to-day and which is shown as the second of two 



