Mr.Grauam on Phosphuretted Hydrogen. 93 
tion of all others, and even of hydrogen and sulphuretted hydro- 
gen themselves above a certain proportion, distinctly impeded or 
destroyed the accendibility of this gas. Thus, one volume phos- 
phuretted hydrogen ceased to be spontaneously inflammable when 
mixed with the following proportions of different gases :— 
With 5 volumes hydrogen, 
2... carbonic acid, 
3... nitrogen, 
1 volume olefiant gas, 
3... sulphuretted hydrogen, 
- po «++ nitric oxide, 
- gy +.  muriatic acid, 
+... ammoniacal gas. 
It is to be remarked, however, in reference to the preceding 
table, that some specimens of phosphuretted hydrogen appear to 
be more highly accendible than others, and that there is consi- 
derable latitude in the proportion of foreign gas which may be 
requisite for destroying the spontaneous inflammability of a given 
specimen. Often a much smaller portion suffices than is stated 
in the table. I have found half a volume of carbonic acid or of 
nitrogen to produce the: effect. Of course the introduction of 
any trace of air, with the gases, must be carefully guarded against. 
Nitrous acid, when present in hydrogen in too small a proportion 
to enable that gas to communicate spontaneous inflammability to 
phosphuretted hydrogen, or to be perceived by the smell, may 
be detected by the effect of the hydrogen upon a prepared mix- 
ture of non-accendible phosphuretted hydrogen and air, which 
mixture may be had quite free from white smoke, and transpa- 
rent. The addition of hydrogen to this mixture occasions the 
immediate appearance of a dense white smoke, the oxidation of 
the phosphorus being partially induced, if even an infinitesimal 
proportion of nitrous acid exist in the hydrogen. Although the 
oxidation of the phosphorus takes place at the expense of the air 
present, and only when air is present, yet the nitrous acid: appears 
