94 NON-METALS AND THEIR COMBINATIONS. 



upon the surface of the phosphorus soon raising it to 60, 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 bisulphide of car- 

 bon, 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 3 ; 

 quinquivalent in others, as in PC1 5 , P,0 5 . 



The molecules of most elements contain two atoms; phos- 

 phorus 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 temperature of 240 to 250, in an atmosphere of 

 carbon dioxide. Phosphorus is thereby gradually converted 

 into a red powder, which differs widely from common phos- 

 phorus. It is not poisonous, not luminous, not soluble in the 

 solvents above mentioned, not combustible before it has been 

 heated to about 280, when it is reconverted into common phos- 

 phorus. 



Use of phosphorus. By far the largest quantity of all phos- 

 phorus (both common and red) is used for matches, which are 

 made by dipping the wooden splints into some combustible sub- 

 stance, as melted sulphur or paraffin, and then into a paste, 

 made by thoroughly mixing phosphorus with glue in which 

 some oxidizing agent (potassium nitrate or chlorate) has been 

 dissolved. 



Pharmaceutical preparations containing phosphorus in the 



