254 ON EXPLOSIONS IN CHEMICAL LABORATORIES. 
fused and gas was escaping, an explosion took place, which 
fortunately did not injure the experimenter. It is probable 
that a piece of the cork, which had begun to be charred, 
had fallen into the fused salt. 
Explosions in experiments with Marsh's apparatus, when 
the jet of gas is ignited before all the atmospheric air is 
expelled, have also occurred. It is necessary to observe, 
that on all occasions, when it is intended to ignite the 
evolved hydrogen gas, care must be taken to allow sufficient 
time to elapse for all the atmospheric air to be expelled 
from the apparatus, or at least that so little may be left, that 
the mixture be incapable of exploding. 
Explosions in operations with cyanide of potassium and 
ferridcyanide of potassium are rare, and the following, 
therefore, are worthy of notice : — A chemist had prepared 
cyanide of potassium by Liebig's method, but as the latter 
portions of it were bluish grey, and showed several 
spots containing iron, he attempted to purify a small por- 
tion by fusion. A violent explosion ensued, and the cruci- 
ble was blown to atoms. The contents of the crucible were 
so entirely scattered, that the collected residue did not 
suffice to discover by a chemical examination, the cause of 
this unexpected phenomenon. 
Dr. Eisner has described the following explosion, that 
occurred in preparing ferridcyanide of potassium. Chlorine 
gas hadjbeen passed into a rather large quantity of an aqeousu 
solution of the ferrocyanide of potassium. The gas was 
developed from common salt, sulphuric acid, and the oxide 
of manganese, in cast-iron vessels. In the course of the 
operation it was discovered that after some time a large 
quantity of muriatic acid was developed, in consequence of 
which the mixture was set aside and replaced by a fresh 
one. In the vessels in which the gas had been developed 
a brownish red, hard, stone-like mass was contained. This, 
upon examination, was found to contain chloride of iron 
and some undecomposed oxide of manganese, which, as it 
