58 



PRINCIPLES OF CHEMISTRY. 



matter ; yet they are of interest and importance on account of 

 being used in their elementary state, or in the form of different 

 compounds in every-day life for various purposes. 



A third number of elements are found in such minute quan- 

 tities in nature that they are almost exclusively of scientific in- 

 terest. The existence of some elements, the discovery of which 

 has been claimed, is even doubtful. 



The elements enumerated in column I. are those of great and 

 general interest ; in II. those claiming our interest on account 

 of the use made of them ; in III. those having scientific interest 

 only. 



I. 



Aluminium 



Calcium 



Carbon 



Chlorine 



Hydrogen 



Iron 



Magnesium 



Nitrogen 



Oxygen 



Phosphorus 



Potassium 



Silicon 



Sodium 



Sulphur 



Classification of elements may be based upon either physical or 

 chemical properties, or upon a consideration of both. A very 

 natural classification of all elements is the one dividing them 

 into the two groups of metals and non-rnetals. 



