320 



SMITH'S INTERMEDIATE CHEMISTRY 



and coke, and heating the mixture in an electric furnace (Fig. 

 85). The mixture is admitted by moving the traps below the 

 hopper, and is carried into the furnace by the worm conveyor. 

 The resistance of the mass between the electrodes causes great 

 development of heat. The actions may be shown by partial 

 equations, which, when added together, give the complete equa- 

 tion: %,^* / 



Ca 3 (P0 4 ) 2 -3CaO + P 2 6 

 3CaO -fj5Si0 2 -3CaSi0 3 (calcium silicate 

 P 2 O 6 + 5C->2P4-5CO 



Ca 3 (P0 4 ) 2 + 3Si0 2 + 5C - 3CaSi0 3 J, + 2P | + SCO | . 



The calcium silicate is melted and runs out below as a slag. The 

 phosphorus (vapor) and carbon monoxide 

 (gas) pass off through the opening near the 

 top. The phosphorus vapor is condensed 

 under cold water. 



White Phosphorus. The product, after 

 purification, is a colorless, transparent waxy 

 solid (sp. gr. 1.83), which melts at 44 and 

 boils at 287. It is insoluble in water, but 

 dissolves in carbon disulphide. It has a 

 strong odor, resembling ozone. 



White phosphorus oxidizes in the air, giv- 

 ing, when moist, phosphorous acid and phosph'oric acid, and 

 emitting a faint light from which the element derives its name 

 (Greek, light bearer"). It catches fire at a low temperature (about 

 35), and in burning forms a cloud of the "solid phosphorus 

 pentoxide P 2 5 . It combines readily, even when cold, with the 

 halogens, and when heated it unites with sulphur and the more 

 active metals. 



^Whitejphosphorus is a very active poison. (fatal dose, 0.15 g.). 

 When traces of the vapor are breathed day after day, a disease, 



FIG. 85 



