356 Experiments on Prussic Acid. {May, 
| 
: 
Half a volume of hydrogen...... = 0°0366 
Half a volume of azote ........ = 0°4845 
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ME TE sw cree ech clone Gere oe aed oats 
Thus, according to the preceding analysis, the density of prussic 
vapour is 0°9371, and I found it by direct experiment 0°9476. Not- 
withstanding this difference of 0°01 which exists between these two 
numbers, and which may be an error in the experiment, I think 
that we ought to consider it as demonstrated that prussic vapour 
contains one volume of the vapour of carbon, half a volume ofazote, 
and half a volume of hydrogen, condensed into one volume, and 
that no other substance enters into its composition. 
It is now easy to explain the diminution of volume produced by 
the electric spark in a mixture of prussic vapour and oxygen. It 
ought to be equal to 14 volume of vapour, since that quantity of 
oxygen has disappeared. But half a volume of azote becomes free. 
This reduces the apparent diminution to three-fourths of a volume of 
the prussic vapour, or to 75 per cent. I found it 78°5. But as it 
appears demonstrated that azote and oxygen disappear during the 
combustion of the prussic vapour, to form nitric acid, this affords a 
sufficient explanation of the excess in the diminution. That this 
excess is not exactly proportional to the azote and oxygen which 
have disappeared, must be ascribed to the unavoidable errors of 
experiment. 
The nature of prussic acid appears to me, then, perfectly known. 
But if any doubts remain, they will be removed by the following 
analysis. 
I made about two grammes (30°88 grains) of prussic vapour pass 
slowly through a red-hot porcelain tube over 0°806 gramme (12°45 
grains) of harpsicord wire rolled in the form of a very short cylinder. 
1 obtained two products, a gaseous mixture composed of equal 
volumes of azote and hydrogen, and charcoal, a part of which was 
deposited on the iron, and another intimately combined with it. 
The gaseous mixture contained no carbon ; for after its detonation 
with oxygen, potash produced no diminution in it. I observed that 
the charcoal was deposited only in that part of the tube which con 
tained tke iron, though it occupied only a smail portion of it, and 
though the prussic vapour experienced a very high temperature 
before coming tothe iron. It is true that the carbon, being united 
to the iron, we may ascribe the decomposition of the acid to the 
affinity of this metal for carbon; but as there is a great quantity 
which merely adheres to the metal, this explanation is not sufficient. 
Prussic vapour appears to.me to act the same part as ammonia, 
which, according to the curious remark of Thenard, supports a 
very high temperature in a porcelain tube without being decom- 
posed, and which is decomposed with the greatest facility even at a 
much lower temperature, when it comes in contact of a metal, to 
which, however, it communicates nothing, 
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