PHOSPHORIC ACID. 7 



tain 2-440 kg., say 5^ lb. But a human body weighs, on an aver- 

 age, 75 kg., say 165 lb. ; deducting the weight of the skeleton there 

 remains 70 kg., say 154 lb. of soft parts, which on incineration yield, 

 like ox-beef, 1*5 per cent of ash entirely composed of phosphate of 

 soda, potash or lime, and alkaline chlorides. The amount of phos- 

 phoric acid which they contain may be taken as equal to an amount 

 of phosphate of lime equal to 80 per cent of the weight of the ash, 

 or to 1-5 per cent of the weight of the soft parts multiplied by 0-8, 

 say 840 grm. These 840 grm. added to the 2-440 kg. contained in 

 bones, give a total of 3-28 kg. of phosphate of lime, say 1-439 kg. of 

 phosphoric acid or 639 grm. of pure phosphorus. These figures show 

 the importance of the role which phosphoric acid plays in the support 

 of the globe. They ought to teach us also to use, with wise fore- 

 sight, the stores of phosphoric acid with which bygone ages have 

 endowed us, because, whatever may be the importance of the deposits 

 now knowm and exploited, and even of those w^hich may be discovered 

 in the future, they are far from being inexhaustible ; besides the danger 

 of dispersion of phosphoric acid by default of restitution to the soil 

 actuahy exists, more threatening for a future less distant than that 

 of the dispersion of nitrogen and potash. 



Properties of Phosphorus — (1) Physical Properties. — Phosphorus 

 obtained by Scheele's method, i.e. by the distillation of phosphate 

 of hme and charcoal, is a colourless yellow translucent body. It is 

 found in commerce mainly as sticks. At the ordinary temperature 

 it is soft like w^ax, brittle in the cold. It has the odour of garlic. 

 Its density varies bet^veen 1-82 and 1-84. It is insoluble in water 

 and in alcohol, very soluble in essential oils, ether, benzol, carbon 

 disulphide, sulphur chloride, and phosphorus chloride.^ Phosphorus 

 melts at a temperature of 44 -z" C. and forms a colourless, oily liquid ; 

 if melted phosphorus be rapidly cooled it is converted into a black 

 mass w^ith a metallic appearance ; if, on the contrary, the molten 

 mass be still further heated — up to a temperature of 250-260° C. — 

 it is converted into a red modification w^hich, at 280° C, reverts to the 

 ordinary form. Phosphorus is highly poisonous. The absorption 

 of a few centigrammes suffices to produce the death of a man by 



^ The solution of phosphorus in carbon disulphide was used by the Irish 

 Fenians to burn the farms of their countrymen who were refractory to the Land 

 L i'rigue. This solution evaporates spontaneously and leaves phosphorus in a state 

 of extreme division. The phosphorus then inflames spontaneously. If wooden 

 objects be coated with a solution of Fenian fire nothing can prevent a confiagra- 

 tion. The solution of phosphorus in carbon disulphide, mixed with sulphur 

 chloride, can be preserved well in close vessels but inflames with violence if a few 

 drops of ammonia are allowed to fall thereon. This is the Lorraine tire of 

 Nickles of 1869. Care must be taken to work in the open air on small quan- 

 tities and to pour the ammonia by aid of a long tube. The new Lorraine tire of 

 P. Guyot, 1871, is a solution of phosphorus in carbon disulphide to which sulphur 

 bromide has been added. It inflames in 1 or 2 minutes after ammonia has 

 been added. 



