Mr Grauam 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 Nitrie Oxvide.—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 
