CHAPTER XIII 

 Phosphorus and Its Compounds 



104. Occurrence. Phosphorus is found in nature in 

 combination with oxygen and other elements, forming 

 phosphates, as Ca 3 (POJ 2 . It is never found in a free or un- 

 combined condition. In soils, it is found in small amounts, 

 and in many rocks and minerals, as apatite or phosphate 

 rock, it is present in large amounts ; it is also found in the 

 ash of plants, and in animal bodies, particularly as a con- 

 stituent of bones. 



105. Preparation. It is prepared from bones, which 

 are first freed from organic matter by burning. The 

 bone ash is treated with sulfuric acid, producing acid 

 phosphates, which, when roasted with charcoal, liberate 

 free phosphorus. 



106. Properties. There are two forms of phosphorus: 

 the yellow and the red. Yellow phosphorus is a solid 

 which ignites at a low temperature. Red phosphorus is 

 an allotropic form of the element produced by heating the 

 yellow variety in a sealed tube. Yellow phosphorus 

 more readily combines with oxygen than does the red, 

 and is kept under water to prevent contact with air. 



107. Oxids of Phosphorus. When phosphorus is 

 burned in a current of oxygen or dry air, phosphorus 

 pentoxid, P 2 O 5 , is obtained. This material is a white 

 flocculent mass which readily dissolves in water, forming 

 metaphosphoric acid. When phosphorus is burned in a 



