Mr Graham on Phosphuretted Hydrogen. 101 



cury, and nitric oxide, charged with nitrous acid, is collected, 

 which may be diluted with hydrogen as above. 



The preceding processes uniformly afford a nitrous impreg- 

 nating mixture which may be depended upon ; but when the ex- 

 periment 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 hydrogen 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 proportion 

 most efficacious, is somewhere between 1 part nitrous acid to 

 1000, and 1 to 10,000 phosphuretted hydrogen. One volume 

 nitrous acid-vapour to 100 gas, or to less gas, is never accendible, 

 but becomes so on diluting it with enough of phosphuretted hy- 

 drogen. 



I was anxious to discover how far nitric oxide interferes in 

 the phenomenon. The nitrous acid is never free from, but always 

 accompanied with, a certain proportion of this gas. 



9. Action of Nitric Oxide. — In a table formerly given, nitric 

 oxide is set down as incompatible with 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 quantity from two volumes to one-tenth of a volume, 

 exhibited no symptoms of spontaneous inflammability. The ni- 

 tric 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 mixture of 

 one volume nitric oxide, with twenty volumes good phosphuretted 

 hydrogen (self accendible per se), is still self accendible ; the 



