PHOSPHOEUS. 



187 



Fig. 81. 



with powdered charcoal, and when the mixture is dry it is 

 put into a stone-ware retort, a, 

 Fig. 81, to the neck of which is 

 attached a copper tube, , the 

 mouth of which dips under wa- 

 ter in a vessel. The retort be- 

 ing subjected to a white heat, 

 the charcoal unites with the 

 oxygen of the phosphoric acid 

 to form carbonic oxide, and the 

 disengaged phosphorus be- 

 comes vaporized. The vapor 

 and the gas pass over together 

 through the tube, b, the phos- 

 phorus becoming condensed 

 and dropping into the water, and the gas passing out 

 through the small tube in the vessel. Phosphorus is com- 

 monly in the form of small round sticks, this form being 

 given to it by melting it in glass tubes in warm water. 



254. Diffusion of Phosphorus in Nature. Phosphorus is 

 quite widely diffused, not as phosphorus, for it is never 

 found as an element, but in combination with other sub- 

 stances. There is in the body of an adult man from 500 to 

 800 grammes of phosphorus. It is not all in the bones, but 

 there is some in the blood and the flesh, and especially in 

 the brain. Now the phosphorus that is in animals must 

 come from vegetables, and these must get it from the min- 

 eral world. The phosphate salts appear in all kinds of 

 grain, and in leguminous and many other plants, especially 

 in their seeds. If there were no such salts in the soil these 

 seeds could not be produced, and hence in part the great 

 usefulness of bones, in many cases, as a manure, supplying 

 the deficiency of these salts in the soil. From all this 

 you see that phosphorus has a wide and constant circula- 



