PHOSPHATES'. 437 



(/.) Phosphorus is purified by straining it through leather under 

 hot ivater; or better by distillation in vessels filled with hydrogen gas. 

 It is melted under hot water, in a retort, and suffered to congeal ; the 

 retort is then filled with hydrogen gas, its mouth plunged into warm 

 water, and the distillation is performed by a sand heat or even by a 

 naked fire : it is a delicate and difficult process ; I have been suc- 

 cessful with it, but have had the retort break from the regurgitation 

 of the water ; in such a case there is a violent and even dangerous 

 combustion. 



(m.) It is cast into sticks in the throat of a funnel, or drawn up 

 into tubes by suction ; the finger, protected by leather, is slipped 

 over the end of the tube, and the latter is then placed in cold water. 



(n.) Phosphorus may be obtained by precipitating the phosphoric 

 acid from urine, or from phosphate of soda, by nitrate or acetate of 

 lead; we distil the concrete residuum with charcoal. About 14 or 

 18 parts of phosphorus are afforded by 100 parts of phosphate of 

 lead ; less heat is necessary in this than in the process with bones. 



(o.) The product of phosphorus is greatest ivhen the materials are 

 dry and the distillation is slow. Pelletier obtained 60 ounces at one 

 operation, from the acid of 36 Ibs. of bones, (576 ounces,) decom- 

 posed by 30 Ibs. of sulphuric acid ; at another time he procured only 

 half this quantity. 



(p.) Phosphorus is purified by liquid chlorine. It should be pre- 

 viously granulated, which is done by melting it beneath water and 

 shaking it as the water cools ; then by shaking it in solution of chlo- 

 rine the color is in a few minutes removed.* 



PHOSPHATE OF BARYTA. 



1. PREPARATION. The muriate or nitrate of baryta, mixed with 

 the phosphate of soda or ammonia, produces a precipitate of phos- 

 phate of baryta. 



* By estimates made thirty years ago, the acids which decompose the phosphate of 

 lime, take up uo more than _*_"_ of the lime it contains, and separate from it less 

 than half the phosphoric acid ; " 100 parts, treated by an acid, afford only .33 of 

 acidulous phosphate of lime, containing only .17 of disengaged phosphoric acid out 

 of the .41 of this acid which exists in the 100 parts of phosphate of lime ; so that 

 by the distillation of this substance with charcoal, we obtain only about .05 of 

 phosphorus, instead of .16 which exist in the 100 parts of the bases of bones." It 

 would seem, however, (o.) that Pelletier obtained double this quantity. Neutral 

 phosphate of lime remains in the retort after the distillation of phosphorus ; its 

 origin is obvious. We decompose no more phosphoric acid than what goes to hold 

 in solution the phosphate of lime. In the process of the older chemists, the solid 

 extract of urine was distilled to obtain phosphorus ; only the phosphoric acid of the 

 phosphate of ammonia was decomposed by the combustible matter present, and 

 therefore very little phosphorus was obtained ; the product is increased by the ad- 

 dition of charcoal. 



