52 ELEMENTS OF AGRICULTURE 



the ashes of all plants. Wood ashes are often leached 

 with water and the compounds of potassium and sodium 

 which dissolve out, form common lye, which is used to 

 make soap. 



52. Calcium. — A solid element which never occurs in 

 a free state, but always combined with some other ele- 

 ment. With carbon and oxygen it forms a compound 

 which is properly known as calcium carbonate. 

 When this compound is heated very hot the carbon and 

 part of the oxygen are driven off as carbon dioxide, and 

 the calcium and part of the oxygen remain as quick 

 lime.. Quick lime takes up water very rapidly and 

 changes to slacked lime. Calcium in some form is 

 found in the ashes of all plants. 



53. Magnesium. — This element is a metal of a light 

 silver color. It unites with oxygen when heated, and 

 the union gives a very brilliant light, known as magne- 

 sium light. This light is used for making photographs 

 at night, and the magnesium used for this purpose is 

 called flashlight powder. In the ashes of plants 

 magnesium always occurs combined with some other ele- 

 ment, and never as a metal. 



54. Iron. — This element is so well known that it 

 scarcely needs a description. It is found in the ashes of 

 all plants combined with some other element. The 

 green coloring matter of plants contains iron. 



55. Manganese. — This is a metal that somewhat re- 

 sembles iron. It is seldom found alone, but usually in 

 combination with oxygen. Its compounds are similar 

 to those of iron, and occur in small Quantities in the 

 ashes of all plants. 



