1816.] Experiments on Prussic Acid. 357 
’ The iron in our experiment had become very brittle. Being com- 
bined with charcoal, and entirely surrounded with it, there was no 
probability that it contained oxygen. But to decide the point, 1 
dissolved it in muriatic acid, comparatively with a determinate 
weight of the same iron wire. I obtained a volume of hydrogen 
gas equal to +4 of that which the same wire would have given in a 
state of pure iron. ‘There remained a quantity of carburet of iron 
weighing 0°155 gramme (2°39 grains). This, being calcined with 
red oxide of mercury, was reduced to 0:076 gramme (1°17 grain). 
This quantity of oxide represents +3 of hydrogen. Thus I obtained 
42%. The loss --4 is too small to indicate the presence of oxygen 
in prussic acid. It may be very well ascribed to the experiment. 
These results appear to me to demonstrate that prussic acid con- 
‘tains equal volumes of hydrogen and azote, and that it contains no 
oxygen. ‘To determine the quantity of carbon combined with these 
two bodies, I passed prussic vapour over the brown oxide of copper 
almost at a red heat. The vapour was entirely decomposed, the 
copper was reduced, and drops of water appeared in the tube. The 
gases disengaged, and which were collected over mercury, were a 
mixture of two parts carbonic acid and one part azotic gas. ‘This 
result, taken along with the preceding, demonstrates the nature of 
prussic acid, and confirms the analysis of it made by the eudiometer. 
This process, which I employed only after the first analysis, is so 
simple that it may be exhibited even in a lecture. 
Thus from these analyses it appears evident that prussic acid is 
composed of 
One volume of the vapour of carbon. 
Half a volume of hydrogen. 
Half a volume of azote. 
condensed into one volume ; or in weight of 
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This acid, when compared with other animal substances, is dis- 
tinguished by the great quantity of azote which it contains, by its 
small quantity of hydrogen, and especially by the absence of oxygen. 
Its acid properties cannot depend upon the hydrogen, which is very 
alkalifying, but upon the carbon and azote. We ought to consider 
it as a true hydracid, in which the carbon and azote supply the 
place of the chlorine in muriatic acid, the iodine in hydriodic acid, 
and the sulphur in sulphureted hydrogen ; but this assertion requires 
a fuller elucidation. 
I have likewise attempted to decompose prussic vapour mixed 
with hydrogen by means of electricity. After having passed through 
it at least 50,000 sparks, all the vapour was not decomposed, and 
that which was had more than doubled its volume, The. platinum 
4 
