ON AN EXPLOSIVE COMPOUND, ETC. 
327 
which the deposit had subsided. The fragments of the retort 
were also entirely dispersed — tradition says, " they were no 
where to be found." The laboratory man in alarm rushed 
into the apartment, and was in great danger from the hydro- 
cyanic vapor, when he was hastily removed. 
The circumstance is curious, as presenting the formation of 
this dangerous substance where it was quite unlooked for ; 
and, although the fulminic acid appears to be isomeric with the 
cyanic, it is rather difficult to account for the formation of an 
oxygen acid united with an oxide, from the elements con- 
cerned, viz.: bichloride of mercury, bicyanide of mercury, 
and hydrochloric and hydrocyanic acids, unless in some way 
water had been decomposed, and the hydrogen liberated or 
disposed of. The bicyanide was prepared by boiling red pre- 
cipitate with Prussian blue; whether, in this instance, well 
crystallized salt only was employed, I cannot now say, but 
on considering the subject, I strongly incline to the opinion, 
that nitric acid must have been present, probably from its not 
having been perfectly expelled in the preparation of the red 
precipitate. 
While on this subject, I will advert to a remark common 
in early chemical works, that hydrocyanic acid has the pro- 
perty of expanding to five times its bulk any gas with which 
it may be mixed, and that many dangerous explosions have 
arisen from this cause, on which account capacious vessels 
are directed to be employed in its preparation. I have never 
observed any such mischievous expansibility in the ordinary 
form in which it comes over, and should explosions have 
arisen from the concentrated acid, I should rather apprehend 
it might have arisen from its passing into the gaseous state by 
change of temperature in vessels not large enough to allow 
of its expansion, or not strong enough to bear it, rather than 
from any mysterious propensity of outriding any other gas 
with which it may come in contact. Another conjecture 
arises, whether these early operators may not have encoun- 
tered unawares, some of these dangerous fulminates or ni- 
trurets. — Ibid. 
