130 



PRINCIPLES OF CHEMISTRY. 



fact, that one and the same element has different properties in certain 

 modifications, is, that either the molecules or the atoms within the 

 molecules are arranged differently. Ozone, for instance, has three 

 atoms of oxygen in the molecule, while the common oxygen molecule 

 contains but two atoms. 



Most of the elements are tasteless and odorless ; a few, however, 

 have a distinct odor and taste, as, for instance, iodine and bromine. 



FIG. 36. 



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Diagram of periodic system in spiral form. 



Relationship between elements and the compounds formed 

 by their union. The properties of the compounds formed by the 

 combination of elements are so various that it is next to impossible 

 to give any general rule by which they may be indicated. It may 



