PHOSPHORUS. 177 



principally, of gelatine and phosphate of lime. The 

 individual constituents are gelatine, lime, oxygen, and 

 phosphorus. To obtain the phosphorus, all the rest 

 are to be first removed. Fire removes the gelatine, 

 oil of vitriol the lime, and charcoal, the oxygen. 

 Give the com- 433. The bones, having been previously 

 piete process, burned, the ground ash is mixed with di- 

 lute sulphuric acid and water, and, after several hours, 

 filtered. Sulphuric acid unites with the lime, forming 

 an insoluble sulphate, and at the same time sets the 

 phosphoric acid at liberty, The solution containing 

 phosphoric acid is then mixed with 

 charcoal, and heated in an earthen 

 or iron retort. The carbon takes the 

 oxygen, and passes out of the retort with it, 

 as gaseous carbonic oxide. The phosphorus which is 

 left, being vaporized by the heat, is also expelled, but 

 is reconverted into solid phosphorus by the cold water 

 into which it passes. The figure will give some idea 

 of the arrangement. The neck of the earthen retort 

 passes into a copper tube, which leads into water. The 

 gas produced by the process bubbles through the water 

 and escapes, while the phosphorus is hardened by it, 

 and remains. The mass thus obtained is melted under 

 water, and run into moulds. 



434. PHOSPHORESCENCE. This term is 

 phorescence?~ applied to the luminous appearance of sea- 

 water when agitated, and to other faint 

 light, unaccompanied by perceptible heat. It is ob- 

 served when an ordinary friction match is rubbed upon 



the hand in the dark. The light is owing to a slow 



8* 



