98 Mr Granam on Phosphuretted Hydrogen. 
stroys the spontaneous inflammability, but requires a period of 
not less than twenty or thirty hours. 
Olefiant gas has a negative influence of quite a different cha- 
racter, which has already been alluded to, and which is in action 
the moment the gases are mixed, but which does not appear un- 
less the proportion of olefiant gas be very considerable. It is 
probable that ether-vapour and the gaseous hydrocarburets like- 
wise haye an influence of the same kind. An astonishingly mi- 
nute quantity of an essential oil suffices to destroy the inflamma- 
bility of the gas over mercury, if allowed an hour or two to act. 
Hence it is very difficult to preserve gas in the inflammable con- 
dition, in the mercurial trough, if any portion of the mercury has 
been soiled by an essential oil. 
7. The action of potassiwm on the peculiar principle is equally 
remarkable. A most minute quantity of this metal, or of its 
amalgam, destroys the self-accendibility of the gas in a few mi- 
nutes, without occasioning any sensible reduction of volume that 
could be measured. 
The fact is, potassium, or its amalgam, is without effect upon 
phosphuretted hydrogen itself, at the temperature of the air, 
neither absorbing nor decomposing the gas ; but upon the pecu- 
liar principle the action of this metal is rapid and certain. One 
grain of potassium, amalgamated with fifty pounds of mercury, 
rendered that large quantity of mercury quite unfit for retaining 
gas over it, in the self-accendible condition, for more than a few 
minutes. In such experiments the interference of naphtha 
vapour was perfectly excluded. Zine and tin, either by them- 
selves or in the state of amalgam, have no sensible effect upon 
self-accendible gas, at least in a period of five or six hours. Pro- 
toxide of mercury speedily withdraws the peculiar principle, but 
afterwards also reacts slowly upon the gas itself. On the other 
hand, the peroxide of the same metal is nowise injurious to 
the self-accendible gas. Arsenious acid in powder acts in the 
same manner as protoxide of mercury. The solution of proto- 
