Mr Grauam on Phosphuretted Hydrogen. 99 
sulphate of iron, if previously boiled to deprive it of air, is with- 
out effect: upon the gas. 
The extraordinary action of potassium, and that also perhaps 
of the essential oils, seemed to point to the existence of an oxy- 
genated principle, as the cause of the spontaneous inflammabi- 
lity of phosphuretted hydrogen. 
It is sufficiently evident that) the proportion in which this 
principle exists to the whole gas, is exceedingly small, too minute 
to afford any hope of isolating that principle. The nitrous im- 
pregnation, too, which was found adequate to.render gas sponta- 
neously inflammable, shews to how minute a quantity of matter 
the spontaneous inflammability of phosphuretted hydrogen may 
at times be owing. It seemed within the bounds .of possibility 
that the gas might owe its spontaneous inflammability, in ordi- 
nary circumstances, if not to nitrous acid, at least to some other 
principle analogous to that substance. This led toa careful exa- 
mination of the properties of phosphuretted hydrogen made in- 
flammable by means of nitrous acid ; a subject of much interest, 
as illustrating the effect of a most minute and almost. infinite- 
simal quantity of foreign admixture, in communicating so strik- 
ing a property as spontaneous inflammability to a chemical body, 
independently of the light which it may throw upon the consti- 
tution of ordinary phosphuretted hydrogen. 
8. Phosphuretted hydrogen, which had lost all trace of spon- 
taneous inflammability by standing a day or two over water, or 
the gas from hydrated phosphorous acid, might be impregnated 
with nitrous acid, and made spontaneously inflammable in vari- 
ous ways. It was ascertained that the gas obtained, by either 
process, was affected in the same way. Such gas only, entirely 
destitute of spontaneous inflammability, was employed in the fol- 
lowing 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 
N2 
