PHOSPHORUS. 



the seleniates have of detonating when ignited with charcoal, 

 and causing a disengagement of chlorine when heated with 

 hydrochloric acid. To separate the selenic from the sulphuric 

 acid, Berzelius recommends the saturation of the acids with 

 potash, and the ignition of the dried salt, mixed with salam- 

 moniac ; the selenic acid is decomposed by the ammonia and 

 reduced to the state of selenium. 



SECTION XI. 



PHOSPHORUS. 



Eq. 392.28 or 31.44 (196.14 or 15.72 according to Berzelius 

 and Turner ;) density of vapour 4327 j \ ! 



This remarkable element appears to be essential to the or- 

 ganization of the higher animals, being found in their fluids, and 

 forming in the state of phosphate of lime, the basis of the solid 

 structure of the bones. It is also found in most plants, and 

 in a few minerals. Phosphorus was first obtained by Brand of 

 Hamburgh in 1 660, but Kunkel first made public a process for 

 preparing it, which was afterwards improved by Margraff and 

 by Scheele. Its ready inflammability, from which phosphorus 

 derived its name, has always made this substance an object of 

 popular interest ; while the singularity, importance and variety 

 of the phosphoric compounds have drawn to them no ordinary 

 share of the attention of chemists. 



Preparation. Phosphorus is not a substance that can be 

 easily prepared on a small scale, but ever since the time of 

 Godfrey Hankwitz, to whom Mr. Boyle communicated a pro- 

 cess for preparing it, phosphorus has been manufactured in 

 London, in considerable quantity and of great purity, for the 

 use of chemists. The earth of bones is decomposed by 2-3rcls of 

 its weight of sulphuric acid, and the insoluble sulphate of lime 

 separated by filtration from the soluble phosphoric acid, which 

 passes through with a quantity of phosphate of lime in solu- 

 tion. The acid liquor is then evaporated to the consistence of 

 a syrup, and mixed with charcoal to form a soft paste, which 

 is rubbed well in a mortar, and then dried in an iron pot with 

 constant stirring till the mass begins to be red hot. It is al- 

 lowed to cool, and introduced as rapidly as possible into a stone- 



z 2 



