PROBLEMS OF MODERN SCIENCE 



effected, and organic chemistry ultimately became 

 merely the branch of chemistry which concerned 

 compounds of carbon. It is true that the distinc- 

 tion between organic and mineral chemistry is by 

 no means sharp, for there are many carbon com- 

 pounds which contain metals, such as mercury or 

 magnesium, and other elements besides carbon, 

 hydrogen, and oxygen, but the separation offers 

 many advantages, and is justified by the peculiar 

 nature of the chemical reactions of carbon com- 

 pounds. 



Before this modified view of organic chemistry 

 became general, the science had made great pro- 

 gress, chiefly with the aid of the fundamental 

 notions of atoms and molecules. Matter, whether 

 gaseous, liquid, or solid, was supposed to consist 

 of small units termed molecules. In any piece 

 of matter which is chemically homogeneous all the 

 component molecules are alike, and the chemical 

 properties of the form of matter are also those of 

 each individual molecule. These molecules are 

 not indivisible ; they are conceived to be clusters 

 of atoms which are the smallest chemical units 

 of matter. Atoms are chemically indivisible and 

 are the smallest units of the chemical elements 

 which can enter into combination with each other 

 to form molecules. In molecules of the elements 

 the atoms are all alike, but the molecules of many 

 complex carbon compounds may consist of as many 

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