CHAPTER XIX 

 Calcium, Magnesium, and Their Compounds 



1 66. Occurrence of Calcium. This element is found 

 widely distributed in nature in the form of calcium car- 

 bonate, CaCO 3 , calcium phosphate, Ca 3 (PO 4 ) 2 , and calcium 

 sulfate, CaSO 4 , and is a yellowish metal which readily 

 oxidizes and decomposes water. It enters into the com- 

 position of both plant and animal bodies and takes an 

 important part in life processes. Its compounds are use- 

 ful in the industries, lime, cement, and mortar being some 

 of the forms in which it is employed. Calcium is not 

 easily separated from its compounds. 



167. Calcium Carbonate. This compound, in the form 



of limestone 

 and marble, is 

 found quite 

 e x t e n s ively . 

 It is soluble to 

 a slight ex- 

 tent in water 

 charged with 

 carbon dioxid, 

 and hence 

 many waters, 



as stated in 



Fig. 56. Section of lime kiln. Section 65, 



owe their hardness to its presence. Calcium carbonate is 

 used principally for the preparation of quicklime, in the 



