" 
ON THE GASES EVOLVED FROM IRON FURNACES. 185 
the existence of one must arise from the destruction of the other. But when 
we view more closely the circumstances under which the cyanogen is pro- 
duced, we are compelled to admit that the ammonia cannot take part in its 
formation. The hearth, at which the formation of cyanogen takes place, is 
the deepest and hottest part of the furnace, and it would be absurd to 
suppose that the coal which reaches this part could contain a trace of am- 
monia, exposed as it has been for eighty hours to a red heat, and in one 
part to a temperature sufficient to reduce potash. Hence we are compelled 
to adopt the only remaining conclusion, that the nitrogen of the air intro- 
duced by the blast combines directly with carbon to form cyanogen. This 
direct formation has been argued for by various chemists, and supported in 
this country by the experiments of Fownes and Young. But as it has been 
objected to experiments of this kind, that they were instituted without refer- 
ence to the ammonia of the air, which is apt to be taken by most substances 
exposed to it, it is searcely to be wondered at that the direct generation of 
ammonia is still doubted by distinguished chemists. We have therefore 
thought it necessary to determine this disputed question by an experiment 
which seems to banish all sources of error. We have led simultaneously, and 
under exactly the same conditions, a stream of carbonic acid and another of 
nitrogen, at a very high temperature, over a mixture of two parts of charcoal 
from sugar and one part of chemically pure carbonate of potash, and have 
subjected the products to careful examination. The apparatus used by us 
in these experiments is represented in fig. 9: a is a gasometer, from which a 
uniform stream of air is made to pass through a bottle filled with sulphuric 
acid (6), and then through a gun-barrel (cc) filled with copper turnings. 
The gun-barrel is kept in a furnace, so that the air passing through it is 
thoroughly deprived of oxygen and passes into the gun-barrel (d d) filled with 
the mixture of charcoal and potash, and heated to a temperature sufficient 
to reduce potassium. In the same furnace is placed another gun-barrel (ee), 
filled with the same mixture, and over which is passed a stream of dry car- 
bonic acid from the apparatus fg. When both the systems were completely 
filled, one with nitrogen, the other with carbonic acid, the streams of gas were 
allowed to pass slowly over the mixture of potash and charcoal, both the 
tubes in the same furnace being kept at a temperature sufficient to reduce 
potassium. The gas passing out of the tube filled with carbonic acid had all 
the characters of pure carbonic oxide, being transparent, inodorous, and 
burning with a pale blue flame, without depositing any kind of sublimate. 
The tube over which nitrogen passed emitted a gas richly laden with a white 
smoke of cyanide of potassium, which sublimed in such quantity as to stop 
the conducting-tube. When the nitrogen was passed so slowly through the 
sulphuric acid that the bubbles passed only once in a second, its absorption 
by the potash was complete, and no gas appeared at the mouth of the gun- 
barrel ; but as soon as the temperature was lowered, so as to be under that 
necessary for the reduction of potassium, the absorption of nitrogen ceased. 
The contents of the tube over which carbonic acid had passed were examined 
after cooling without the detection of the smallest trace of cyanide of potas- 
sium. The mixture treated with nitrogen, on the other hand, dissolved (with 
the exception of its charcoal) with a very powerful odour of hydrocyanic 
acid. The solution exhibited all the reactions of cyanide of potassium, and 
yielded 6:982 grms. of cyanide of silver, which dissolved (with decomposition ) 
in fuming sulphuric acid without leaving any residue of chloride of silver after 
being diluted with water. Hence we cannot for a moment demur to the fol- 
lowing eonclusion,—That a considerable quantity of cyanide of potassium is 
formed: in iron furnaces immediately above the point where the blast comes 
