124 PRINCIPLES OF CHEMISTRY. 



In these formulas we show that sulphur exerts the valence of six, 

 that four of its affinities are saturated by oxygen, while the two re- 

 maining are attached to two oxygen atoms, the unsaturated affinities 

 of which are satisfied by hydrogen. 



9. GENERAL REMARKS REGARDING ELEMENTS. 



Relative importance of different elements. Of the total 

 number of about seventy-six elements, comparatively few (about 

 one-fourth) are of great and general importance for the earth, and the 

 phenomena taking place upon it. These important elements form 

 the greater part of the mass of the solid portion of the earth, and of 

 the water and atmosphere, and of all animal and vegetable matter. 



Another number of elements are of less importance, because either 

 they are not found in any large quantity, or do not take any active 

 or essential part in the formation of organic 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 quantities 

 in nature that they are almost exclusively of scientific interest. Even 

 the existence of some elements, the discovery of which has been 

 claimed, is doubtful. 



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

 eral interest ; in II. those claiming interest on account of the special 

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



I. II. 



Aluminum Antimony Iridiuin 



Calcium Arsenic Lead 



Carbon Barium Lithium 



Chlorine Bismuth Manganese 



Hydrogen Boron Mercury 



Iron Bromine Molybdenum 



Magnesium Cadmium Nickel 



Nitrogen Cerium Platinum 



Oxygen Chromium Radium 



Phosphorus Cobalt Silver 



Potassium Copper Strontium 



Silicon Fluorine Tin 



Sodium Gold Uranium 



Sulphur Iodine Zinc 



