52 THE ELEMENTS OF PLANT FOOD 



As it comes from the mines it is mixed with common 

 salt, gypsum (calcium sulphate), potassium chloride, 

 and other minerals. 



Note. Potassium hydroxide is used to destroy the soft horn form- 

 ing on the heads of calves, thus easily and painlessly dehorning them. 

 Wrap a piece of paper about a stick of KOH to protect the hand, 

 moisten one end of the stick, and rub it on the nub of the horn appear- 

 ing on the head of the calf. Care should be taken that none of the 

 caustic flows down on the skin of the animal. Two applications wili 

 effectually prevent the growth of the horn. 



CALCIUM (Ca) 



Description and Occurrence. Calcium is abundant 

 in the ash of all plants and gives to plants vigor of 

 growth and ability to stand climatic changes and 

 drouth. It is a yellowish white, soft metal, not found 

 free in nature. As a metal it is of little importance, 

 but its compounds are widely distributed on the sur- 

 face of the earth. 



Calcium carbonate (CaCO 3 ) is also called carbonate 

 of lime. This important compound makes up the 

 larger part of limestone and of marble; the shells of 

 oysters and other mollusks are composed almost 

 entirely of it, while in the bones of animals and the 

 shells of eggs it enters as an important ingredient. 

 Water charged with CO 2 dissolves calcium carbonate, 

 producing a bicarbonate of lime. 



CO 2 + H 2 O = H 2 CO 3 

 CaCO 3 + H 2 CO 3 = CaH 2 (CO 3 ) 2 



It is this compound with others that makes what is 

 called hard water. 



Carbonate of lime is found in ample quantities in 



