112 NON-METALS AND THEIR COMBINATIONS. 



phorus volatilizes with the steam, and small globules of it may be found in the 

 collected fluid. If, however, the quantity of phosphorus in the examined 

 matter was very small, it may all have become oxidized during the distillation, 

 and the fluid will then contain phosphorous acid, the tests for which will be 

 stated below. 



FIG. 12. 



Apparatus for detection of phosphorus in cases of poisoning. 



It should be mentioned that the luminosity of phosphorus vapors is dimin- 

 ished, or even prevented, by vapors of essential oils (oil of turpentine, for 

 instance), ether, olefiant gas, and a few other substances. 



Oxides of phosphorus. Two oxides of phosphorus are known 

 in the separate state. They are phosphorus trioxide or phosphorous 

 oxide, P 2 O 3 , and phosphorus pentoxide or phosphoric oxide, P 2 O 5 . The 

 first is obtained by slow oxidation of phosphorus, the second by 

 burning phosphorus in dry air or oxygen. Both oxides are white 

 solids, which combine readily with water, forming the four acids 

 mentioned below. 



No oxides corresponding to hypophosphorous acid, H 3 PO 2 , and 

 hypophosphoric acid, H 2 PO 3 , are known. 



