180 INORGANIC SUBSTANCES. 



Chloride of calcium also has a wonderful eifect 

 upon many crops. 



Sulplmret of calcium is produced by the agency 

 of heat acting upon calcium and sulphur. 



Sulphate of lime. This compound of sulphur and 

 lime is very valuable as a fertilizer, and has caused 

 lands which before had defied all attempts to render 

 them productive to bring forth fine crops. Besides 

 its other properties, it possesses that of absorbing 

 ammonia from the air. 



Nitrate of lime is found in the soil, and is of con- 

 siderable value, but is very soluble. 



Phosphate of lime is the substance from which the 

 bones of animals are formed, and is important as a 

 manurial substance. It is soluble only in acids, 

 when it becomes super-phosphate of lime. 



Chlorine, in combination with hydrogen, forms 

 muriatic acid, which dissolves many of those sub- 

 stances of the soil that are insoluble in water, and 

 prepares them to become the food of plants. 



Iodine is beneficial to vegetation when combined 

 with sodium. It is soluble, and exists largely in 

 the waters of the ocean. 



Oxides of iron. Iron combines in two difierent 

 proportions with oxygen. One is called prot-oxide, 

 and possesses about twenty-three per cent, of oxygen. 

 This is very injurious to plants ; but by exposure 

 to the air it assimilates with more oxygen, and 

 becomes per-oxidc, in which state it is a powerful 

 absorbent of ammonia. 



