CHEMICAL COMPOSITION OF THE SOIL 41 



Sulphur is a pale yellow substance which generally occurs in the 

 soil united with some metal as iron, lime, or magnesia. The 

 characteristic odors of garlic, onions, and some other vegetables 

 are due to the presence of sulphur. It is an essential part of many 

 organic compounds in the tissues of plants and animals. Its 

 presence in eggs is readily shown by its action on silverware, which 

 it blackens. 



Hydrogen is a colorless substance which may be obtained in 

 gaseous form by the decomposition of water. It plays its greatest 

 part in agriculture while combined with oxygen in the form of 

 water, which is so essential to both animal and plant life. 



Chlorine is a greenish yellow substance which has a suffocating 

 odor. It is generally combined with sodium and in this form is 

 known as common salt, which occurs in all soils and natural waters. 

 It is present in most plants and seems to be an essential element. 



Phosphorus is a soft pale yellow substance obtained from bone 

 ash. It is present in several forms in the soil and is an important 

 ingredient. A part of the phosphate found in bone ash and in 

 nature is insoluble in water until treated with sulphuric acid. 



Nitrogen is a colorless substance comprising in gaseous form 

 about four fifths of the atmosphere and is a constituent of animal 

 and vegetable matter. In spite of its great abundance in the 

 air, it is one of the least abundant in the soil. Here it occurs 

 as a part of the humus and the fragments of the decaying tissues 

 of plants and animals. Nitrogen is being constantly taken from 

 the soil in the form of nitrates, and in order to preserve the fertility 

 of the soil nitrogen must constantly be supplied. This is usually 

 done by allowing nitrogenous organic matter to decay upon the 

 soil or by adding to the soil a fertilizer containing nitrogen com- 

 pounds. 



Fluorine is a pale yellow substance which has a powerful odor. 

 United with lime it occurs in fluorite. Fluorine is a constituent 

 of the blood, milk, teeth, and bones of animals. 



Boron. Borax is the most, familiar compound in which boron 

 occurs. In this form it is largely used as a preservative for 

 sausage, canned meats, fish, milk, butter, beer, and wine. Boron 

 is not a very common element, but in the form of borax is found in 

 the United States, principally in California and Arizona. 



