THE ELEMENTS. 33 



cultivated plants, we have arranged them as 

 follows : 



I. Gaseous Elements. Oxygen, Hydrogen, 

 Nitrogen, Chlorine. 



II. Elements combining with Oxygen to form 

 Acids. Silicon, Carbon, Phosphorus, Sulphur. 



III. Elements combining with Oxygen to 

 form Bases. Calcium, Magnesium, Iron, Potas- 

 sium, Sodium. 



The combinations of Potassium and Sodium 

 are termed alkalies. 



The elements unite in definite proportions, 

 called equivalents, representing the smallest 

 quantity in which they enter into comtrination, 

 one with the other. The equivalents are, for 



Oxygen 8 



Hydrogen 1 



Nitrogen 14 



Chlorine 35.5 



Silicon 14 



Carbon ,. 6 



Phosphorus 31 



Sulphur 16 



Calcium 20 



Magnesium 12.2 



Iron 28 



Potassium 39 



Sodium 23 



To render the above intelligible, we give a few 

 examples, viz : 8 pounds or parts of oxygen 

 unite with 1 pound or part of hydrogen, to form 

 9 pounds or parts of water. Three parts of 

 hydrogen unite with 14 parts of nitrogen, to 

 form 17 parts of ammonia; and 16 parts of sul- 

 phur unite with 24 parts of oxygen, to form 40 

 parts of anhydrous sulphuric acid. 



