84 UNIVERSITY OF MISSOURI BULLETIN 



sent molecules, and the arrangement of these units in regular 

 order would represent the crystal, a limited quantity of the 

 substance. 



The idea is that substance is composed of molecules which 

 in crystalline substances like sugar have a definite, symmetrical 

 arrangement, while in non-crystalline substances like wood 

 these units have no such arrangement. 



One of these units, the molecule, is not the substance ; the 

 molecule does not possess the properties of the substance; the 

 properties of the substance are the properties of the aggregate 

 of molecules. There may be other aggregates of the same 

 molecules with the production of other and new substances 

 differing from the first, just as our regiment may still retain 

 its companies, yet the companies may form other units, bat- 

 talions. 



The change from a regiment of companies to a regiment 

 of two or three battalions represents one kind of a chemical 

 change. 



The change may go further still. The company composed 

 of different kinds of soldiers, officers, commissioned and non- 

 commissioned, and men represents the molecule of a com- 

 pound, while the constituent units, the individual men of dif- 

 ferent grades, represent the different kinds of atoms, the con- 

 stituents of the molecule. 



When the molecules take part in a chemical reaction, the 

 units, in this case the atoms, separate and form entirely new 

 groups usually by uniting with atoms separated from mole- 

 cules of another substance taking part and an equal part in 

 the reaction, forming new and dissimilar groups, molecules. 



To continue the analogy, it would be as though companies 

 of infantry, batteries of artillery and troops of cavalry could 

 separate and men from the different companies form new com- 

 panies composed of the same proportions of infantry men, 

 cavalry men and artillery men, the men retaining in their new 

 formations all the arms, accoutrements and manual of the old 



