100 Mr Graham on Phosphuretted Hydrogen. 



the gas. When nitric acid is brought into contact with the gas 

 in this manner, a violent action occurs ; but with nitrons acid the 

 evolution of white fumes is very slight. The nitrous acid is ab- 

 sorbed in part by the mercury, but this absorption is slow, pro- 

 vided the quantity of gas be considerable with which the acid 

 vapour is mixed. If the quantity of gas primarily impregnated 

 with nitrous acid, in the manner described, be small, or the im- 

 pregnation of nitrous acid considerable, the gas exhibits no dis- 

 position to smoke or to take fire, when passed into air. It has 

 not become spontaneously accendible. On diluting the gas with 

 a large proportion of unimpregnatedphosphuretted hydrogen, no 

 reaction is indicated, but the whole becomes spontaneously ac- 

 cendible in a high degree. In fact, it was discovered that the 

 gas is not accendible when the nitrous acid exceeds a certain pro- 

 portion, which is by no means considerable. 



(2.) Allow a single drop of nitrous acid to fall into a dry 

 glass jar, which may be of small dimensions. Fill the jar with 

 mercury, and invert it without loss of time in the mercurial 

 trough, a bubble of gas will collect in the upper part of the jar, 

 which bubble is chiefly nitrous acid vapour. One cubic inch or 

 so of phosphuretted hydrogen, or of hydrogen itself, may then be 

 added to the gas in the jar, and this is our nitrous impregnating 

 mixture. Suppose this mixture to contain one-twentieth of its 

 bulk of nitrous acid vapour. The addition of it, in any propor- 

 tion, to phosphuretted hydrogen, is not attended by the slightest 

 production of white fumes ; in fact no 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 above arrangement, a drop of the strongest nitric 

 acid may be substituted for the nitrous acid, in the preparation 

 of the impregnating mixture. The nitric acid acts on the mer- 



