PHOSPHORUS, ARSENIC, ANTIMONY, BISMUTH 321 



frequently shown by workers in match-factories and consisting in 

 ulceration of the bones of the jaw, makes its appearance. The 

 use of white phosphorus is forbidden by law in Sweden, France, 

 Great Britain, and Switzerland and is penalized by a special tax 

 hi the United States. 



Red Phosphorus. When white phosphorus is heated at 230 

 to 300 in a tightly closed vessel (air excluded) it changes into red 

 phosphorus. This material is composed of small crystals, of dull 

 red color, and variable specific gravity 2.19 to 2.34. It is insoluble 

 in carbon disulphide, has no odor, and is not poisonous. On dis- 

 tillation the vapor condenses to white phosphorus. 



This allotropic form of phosphorus is formed from the white 

 variety with liberation of much heat. It thus contains less energy, 

 and is much less active. It burns to form the pentoxide, but 

 has to be heated to about 240 before it will catch fire in the air. 

 It combines also with elements other than oxygen much less 

 readily than does white 'phosphorus. 



Manufacture of Matches. These are of two kinds, ordinary 

 matches, which strike on any rough surface, and " safety " 

 matches. Ordinary matches are still made in some countries by 

 dipping the splints of wood in melted paraffin, and then in a paste 

 made of 4 to 7 per cent of white phosphorus, lead dioxide about 

 50 per cent, water, and dextrin (paste). The head, when dry, is 

 dipped in varnish to exclude air and moisture. Where the use of 

 white phosphorus is very properly forbidden, a sulphide P 4 S 3 is sub- 

 stituted. When the match is struck, the friction explodes the 

 mixture of phosphorus trisulphide (combustible) and lead diox- 

 ide (or other oxidizing agent), and the resulting heat sets fire to 

 the paraffin and this, in turn, to the wood. 



Safety matches carry no phosphorus, but only a mixture of 

 substances containing oxygen, such as potassium chlorate or 

 potassium chromate, with a combustible, like antimony trisul- 



