Prof. Graham on PhospJmretted Hydrogen. 411 



reaction appears to take place. But the addition of a single 

 bubble of this mixture, not exceeding one tenth of an inch in 

 volume, to five or six cubic inches of phosphuretted hydrogen 

 will render the whole highly accendible, so that every bubble 

 passed into the air will take fire. 



(3.) In the last arrangement a drop of the strongest nitric 

 acid may be substituted for the nitrous acid, in the prepara- 

 tion of the impregnating mixture. The nitric acid acts on 

 the mercury, and nitric oxide charged with nitrous acid va- 

 pour is collected, which may be diluted with hydrogen as 

 above. 



The preceding processes uniformly afford a nitrous im- 

 pregnating mixture which may be depended upon ; but when 

 the experiment is attempted over water, there is not the same 

 certainty of the impregnation being successful. I have often, 

 however, made hydrogen highly suitable for the purpose, by 

 passing it through a column of fluid composed of nitric acid 

 recently diluted with water, provided that the acid had been 

 fuming from the presence of nitrous acid ; or by passing hy- 

 drogen through recently diluted sulphuric acid, as has already 

 been stated. 



In regard to the proper proportion of nitrous acid vapour 

 to the phosphuretted hydrogen, I am satisfied that the pro- 

 portion most efficacious is somewhere between one part ni- 

 trous acid to one thousand, and one to ten thousand phos- 

 phuretted hydrogen. One nitrous acid to one hundred gas, 

 or less gas, is never accendible, but becomes so on diluting it 

 with enough of phosphuretted hydrogen. 



I was anxious to discover how far nitric oxide interferes in 

 the phaenomena. The nitrous acid is never free from, but is 

 always accompanied with, a certain proportion of this gas. 



9. Actionqf Nitric Oxide. — In atable formerly given (p. 405. ), 

 nitric oxide is set down as preventing the accendibility of the 

 good gas from phosphuret of lime, when the proportion of the 

 first is so great as one tenth of the whole mixture. In fact, the 

 best inflammable gas when mixed with nitric oxide in quan- 

 tity from two volumes to one tenth of a volume, exhibited no 

 symptom of spontaneous inflammability. The nitric oxide 

 forms red fumes when the mixture meets the air, but the 

 phosphuretted hydrogen does not even smoke; so that the 

 oxidation of the nitric oxide has not a kindling effect upon 

 the phosphuretted hydrogen, but the very reverse. A mix- 

 ture of one volume nitric oxide with twenty volumes of good 

 phosphuretted hydrogen (self-accendible per se) is still self- 

 accendible ; the bubble, however, does not take fire the instant 

 it bursts in the air, but after rising to a little height, and then 



3 G2 



