Prof. Graham on Phosphuretted Hydrogen. 413 



drogen, it is from the nitrous acid which it occasionally contains 

 It is certainly not a little curious that nitric oxide is not equi- 

 valent to nitrous acid in producing the change in question 

 upon phosphuretted hydrogen, seeing that the nitric oxide 

 passes immediately into nitrous acid upon meeting air. 

 Whether the negative influence of nitric oxide upon really 

 accendible gas is sufficient to account for this anomaly, I am 

 doubtful. It may be thought that nitrous acid and phosphu- 

 retted hydrogen when in contact for a short time, react upon 

 each other, with the production of some entirely new and 

 highly accendible body. But this supposition seems not to 

 quadrate with the fact that the impregnating mixture requires to 

 be diluted by so large a proportion of phosphuretted hydrogen 

 before the whole becomes spontaneously inflammable; nor 

 is it supported by any visible signs of reaction between the 

 nitrous acid and phosphuretted hydrogen. Indeed, nitrous acid 

 vapour appears to be compatible with phosphuretted hydrogen to 

 an extent which could not have been anticipated. Again, that 

 nitrous acid, or at least some acid compound of nitrogen, con- 

 tinues to exist in what we may now call nitrous phosphuretted 

 hydrogen gas, appears to be corroborated by the properties 

 which this self-accendible gas is found to possess. 



10. Properties of Nitrous Phosphuretted Hydrogen. — 

 (1.) This gas loses its self-accendibility when kept over mer- 

 cury, in a period varying from six to twenty-four hours, ac- 

 cording to the amount of nitrous impregnation. It is re- 

 markable that this gas continues in general for a longer time 

 inflammable when confined over water than over mercury, 

 which is the reverse of what occurs with the gas from phos- 

 phuret of lime. 



(2.) The factitious gas is deprived of its spontaneous inflam- 

 mability by charcoal and porous absorbents, by essential oils 

 and hydro-carburets, and by amalgam of potassium, and quite 

 as rapidly as is its natural prototype. 



(3.) Phosphorous acid and concentrated sulphuric acid ap- 

 pear likewise to withdraw the nitrous principle, although 

 phosphoric acid does not. The agency of these acids pro- 

 bably exemplifies the disposition of nitrous acid to combine 

 with other acids. The action of potassium and of essential 

 oils upon nitrous acid requires no explanation. Potassium 

 has, I find, no action on pure nitric oxide in the cold. 



(4.) A cubic inch of this gas, passed up into a receiver of 

 which the inside was moistened with caustic alkali, had its 

 accendibility sensibly impaired in fifteen minutes, but not 

 completely destroyed in less than an hour. 



