Mr Grauam on Phosphuretted Hydrogen. 91 
continues in general spontaneously inflammable over mercury for 
forty-eight hours, and sometimes for three or four days, but ceases 
to be so ina very short time, after the admission of a small pro- 
portion of air, particularly if the air be added in a gradual man- 
ner. Thus, if to the gas be passed up one-twentieth part of its 
bulk of cork or of dry stucco, containing air in its pores, a white 
smoke appears in, the gas, and it ceases to be spontaneously in- 
flammable in the course of afew minutes. The same mass of 
stucco, warmed before being passed up into the gas, so as to ex- 
pel the air it contained, did not, produce the same effect. The 
self-accendible gas always deposits on standing a solid matter con- 
taining phosphorus, of a lively yellow colour, but in quantity too 
minute for analysis. This matter is not acted on by any of the 
ordinary solvents, such as alcohol, ether, alkalies, or muriatic acid, 
but is destroyed by chlorine-water, and by nitric acid. The pre- 
cipitation of this matter is most rapid in the case of gas over 
water, and is indicative of deterioration of the gas. 
2. The self-accendible gas procured from phosphorus, water, 
and lime, is always mixed with free hydrogen, varying in quan- 
tity from 25 to 50 per cent.; while the non-accendible gas from 
phosphorous acid contains no hydrogen gas, but is pure. Roser 
concludes that the spontaneous inflammability of the first species 
cannot depend upon this hydrogen, for the other species is not 
made self-accendible by the addition to it of any proportion of 
free hydrogen. On trying the experiment, however, I obtained 
a different result. A quantity of gas had lost. its self-accendibi- 
lity by standing over water for two or three hours ; to my surprise, 
the addition to this gas of hydrogen, in any proportion from one- 
third of a volume to three volumes, restored the self-accendibility 
of the gas. Spontaneous inflammability was likewise communi- 
cated, in some cases; to the gas procured from phosphorous acid, 
merely by adding hydrogen to it. It was early perceived, how- 
ever, in the course of the investigation, that hydrogen did not 
uniformly communicate the property in question, and that its in- 
M 2 
