96 Mr Granam on Phosphuretted Hydrogen. 
caustic potash, always loses its spontaneous accendibility, although 
by no means rapidly, several hours being generally required. 
5. Certain acids appear to have a remarkable power in with- 
drawing the principle of inflammability from phosphuretted hy- 
drogen. 
Let phosphuretted hydrogen be transferred into a jar inverted 
over mercury, of which jar the inner surface has been moistened 
with concentrated phosphorous acid. A small quantity of a milk- 
white matter immediately appears in the acid, where exposed to 
the gas; and in two or three minutes the gas has ceased to be 
spontaneously inflammable, without any appreciable diminution 
of its volume having occurred. This white matter, although 
very sensible to the eye, exists only in the most minute quantity. 
It is not crystalline, and perhaps is not even solid. The intro- 
duction of concentrated phosphoric acid into the gas, was attend- 
ed by similar phenomena; and the gas lost its spontaneous in- 
flammability in the course of half an hour. 
A strong solution of arsenic acid acts as rapidly in withdraw- 
ing the peculiar principle as phosphoric acid does, but the ar- 
senic acid soon begins to react upon the phosphuretted hydrogen 
itself, a dark copper-coloured incrustation soon forming upon the 
surface of the gas-receiver, which matter is probably a phosphuret 
of arsenic. Concentrated sulphuric acid is capable of absorbing 
phosphuretted hydrogen itself, which the preceding acids are not, 
but even sulphuric acid appears to absorb the peculiar principle, 
in the first instance, by a more active affinity than it exerts up- 
on the gas itself. Dilute phosphorous, phosphoric, and arseni¢e 
acids, react in the same manner upon phosphuretted hydrogen, 
but not so rapidly as the concentrated acids do. 
6. The following liquids are capable of dissolving the quantity 
of phosphuretted hydrogen gas placed against their names, at 
65° Fahr. 
