HO NON-METALS AND THEIR COMBINATIONS. 



equation, as some gaseous hydrogen phosphide and a few other products are 

 formed in small quantities. 



Properties of phosphorus. When recently prepared, phos- 

 phorus is a colorless, translucent, solid substance, which has some- 

 what the appearance and con sistency^of "bleached wax In the 

 course of time, and especially on exposure to light, it becomes by 

 degrees less translucent, opaque, white, yellow, and finally yellowish- 

 red. At the freezing-point phosphorus is brittle ; as the temperature 

 increases it gradually becomes softer, until it fuses at 44 C. (111F.), 

 forming a yellowish fluid, which at 290 C. (554 F.) (in the absence 

 of oxygen) is converted into a colorless vapor. Specific gravity 1.83 

 at 10 C. (50 F.) 



The most characteristic features of phosphorus are its great affinity 

 for oxygen, and its luminosity, visible in the dark, from which 

 latter property its name, signifying "bearer of light," has been 

 derived. In consequence of its affinity for oxygen, phosphorus has 

 to be kept under water, as it invariably takes fire when exposed to 

 the air, the slow oxidation taking place upon the surface of the 

 phosphorus soon raising it to 50 C. (122 F.) at which temperature 

 it ignites, burning with a bright white flame, and giving off dense, 

 white fumes of phosphoric oxide. The luminosity of phosphorus, 

 due to this slow oxidation, is seen when a piece of it is exposed to 

 the air, and whitish vapors are emitted which are luminous in the 

 dark ; at the same time an odor resembling that of garlic is noticed. 



Phosphorus is insoluble in water, sparingly soluble in alcohol, 

 ether, fatty and essential oils, very soluble in chloroform and in 

 disulphide of carbon, from which solution it separates in the form of 

 crystals. 



Phosphorus not only combines directly with oxygen, but also with 

 chlorine, bromine, iodine, sulphur, and with many metals, the latter 

 compounds being known as phosphides. 



Phosphorus is trivalent in some compounds, as in PC1 3 , P 2 O 3 ; 

 quinquivalent in others, as in PC1 5 , P 2 O 6 . 



The molecules of most elements contain two atoms ; phosphorus is 

 an exception to this rule, its molecule containing four atoms. The 

 molecular weight of phosphorus is consequently 4 X 31 = 124. 



Allotropic modifications. Several allotropic modifications of 

 phosphorus are known, of which the red phosphorus (frequently 

 called amorphous phosphorus] is the most important. This variety is 

 obtained by exposing common phosphorus for about two days to a 



