ORGANIC CHEMISTRY 



as five or six different kinds of atoms, according to 

 the number and kind of the elements present. It 

 should be noted that these complex clusters of 

 atoms are not unalterable ; when they are attacked 

 by chemical means they may be added to or 

 broken up, and in either case new molecules are 

 formed, which may be more complex or simpler 

 than the original. 



Investigation of these carbon compounds has 

 shown that some molecules which have quite 

 different chemical properties are composed of the 

 same number and kind of atoms. For example, 

 there are two kinds of molecules composed of two 

 carbon atoms, six hydrogen atoms, and two 

 oxygen atoms. Such cases as this are numerous ; 

 they can be explained only by the assumption 

 that the difference in the molecules results from 

 a difference in the arrangement of the atoms com- 

 posing them. In other words, it is evident that 

 the molecular structure or architecture is different 

 in the two substances. 



The unravelling of the structure of the complex 

 molecules met with in organic chemistry proved 

 by no means a simple matter ; in fact, the modern 

 conception of molecular architecture was attained 

 only after prolonged and tedious research and 

 bitter controversy. The methods used in the 

 earlier work were those of analysis. The pioneers 

 Bunsen, Gay-Lussac, and Liebig showed by their 



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