410 Prof. Graham on Phosphuretted Hydrogen, 



examination of the properties of phosphuretted hydrogen 

 made inflammable by means of nitrous acid; a subject of much 

 interest, as illustrating the effect of a most minute and almost 

 infinitesimal quantity of foreign matter in communicating 

 to a chemical body so striking a property as spontaneous in- 

 flammability. Independently of the light which it may throw 

 upon the constitution of ordinary phosphuretted hydrogen in 

 reference to that property. 



8. Phosphuretted hydrogen which had lost all trace of 

 spontaneous inflammability by standiug a day or two over 

 water, or the gas from hydrated phosphorous acid, could be 

 impregnated with nitrous acid and made spontaneously in- 

 flammable in various ways. It was ascertained that the gas 

 obtained by either process was affected in the same way. 

 Such gas only, entirely destitute of spontaneous inflamma- 

 bility, was employed in the following experiments. 



(1.) The nitrous acid of Dulong may be added directly to 

 the gas over mercury ; a glass spherule, or the bore of a short 

 piece of thermometer tube, being filled with the liquid, and 

 passed up to the gas. When nitric acid is brought into con- 

 tact in this manner with the gas, a violent action ensues, but 

 with nitrous acid the evolution of white fumes is very slight. 

 The nitrous acid is absorbed in part by the mercury, but this 

 absorption is slow, provided the quantity of gas with which 

 the acid vapour is mixed be considerable. If the quantity of 

 gas primarily impregnated with nitrous acid in the manner 

 described be small, or the impregnation of nitrous acid con- 

 siderable, the gas exhibits no disposition 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 

 unimpregnated phosphuretted hydrogen, no reaction is indi- 

 cated, but the whole becomes spontaneously inflammable in a 

 high degree. In fact, it was discovered that the gas is not 

 accendible when the nitrous acid exceeds a certain proportion, 

 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 ni- 

 trous impregnating mixture : suppose this mixture to contain 

 one twentieth of its bulk of nitrous acid vapour ; the addition 

 of it in any proportion to phosphuretted hydrogen is not at- 

 tended by the slightest production of white fumes ; in fact, no 



