HYDROGEN AND PHOSPHORUS. 419 



due to another gaseous compound of phosphorus and hydrogen, 

 P + 2H, present in small quantity, and supposed to be decom- 

 posed by light, and to deposit a solid hydruret P + H, while the 

 gas ceases to be self-inflammable. It was observed by myself,* 

 that the presence of phosphorus vapour does not communicate 

 spontaneous inflammability to the gas prepared from phospho- 

 rous acid ; that the gas from hydrate of lime and phosphorus 

 is deprived of this property by porous absorbents, such as 

 charcoal, by phosphoric acid, and by a most minute quantity of 

 several combustible bodies, such as potassium, the vapours of 

 ether and essential oils ; and that the property was communi- 

 cated to the gas of either process, by the addition of a most 

 minute quantity of the vapour of peroxide of nitrogen or of 

 nitrous acid, varying from 1-lOOOth to l-10,000th of the volume 

 of the gas. The hydrogen gas which first comes off on making 

 an addition of sulphuric acid to the gas bottle with zinc (page 

 257), sometimes contains enough of peroxide of nitrogen, to 

 impart spontaneous inflammability to phosphuretted hydrogen, 

 to which it may be added. The self-inflammable gas from 

 phosphorus and hydrate of lime cannot contain peroxide of 

 nitrogen, but it might be imagined to possess a trace of a cor- 

 responding compound of phosphorus and oxygen, if such a 

 compound exists. 



Phosphuretted hydrogen decomposes some metallic solutions, 

 such as those of copper and mercury, and forms metallic phos- 

 phurets. When the gas is pure, it is entirely absorbed by sul- 

 phate of copper and by chloride of lime. With hydriodic acid, 

 phosphuretted hydrogen forms a crystalline compound, which is 

 interesting from its analogy to sal ammoniac. It may be formed 

 by mixing together its constituent gases over mercury ; or more 

 easily by introducing into a small tubulated retort, a mixture of 

 60 parts of iodine, 1 5 of phosphorus finely granulated, and mix- 

 ing these bodies intimately with pounded glass ; 8 or 9 parts of 

 water are then added to the mixture, and the vapours which 

 immediately come off are allowed to escape by a glass tube open 

 at both ends, adapted to the beak of the retort, in which beau- 

 tiful small crystals of the salt condense, of a diamond lustre. 

 Rose has lately observed that these crystals, contrary to what is 

 generally supposed, do not belong to the regular system, and 



* rbil. Mag. 3rd Scries, vol. 5, p. 401. 



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