1816.]) Experiments: on- Prussic Acid: 355 
prussic vapour accompanies it, anda diminution of voltime takes place, 
which is ascertained-by measuring the residue in a graduated tube. 
This residue, wasbed with a solution of potash or barytes,, experiences 
a new diminution, owing to the absorption of the carbonic acid gas 
formed; Lastly, the-gas which the alkali has left‘is analyzed over 
water by hydrogen, and-it is ascertamed'to be a mixture of azote 
and oxygen, because this last gas-was employed in excess. 
» The white-vapour of which I have spoken appeared ‘to me owing’ 
to alittle nitric acid and vapour of water formed by the combustion; 
for when a little water was introduced. into the eudiometer, after: 
several detonations, it beeame muddy, letting fall oxide of mercury, 
and reddened litmus. 
Supposing we were to operate upon a gaseous mixture containing 
100 of prussic acid ‘vapour, we obtain the following results, which 
are the mean of ' four experiments :— 
VEPOUE fais oesir orinrsise nbavely Kr sisinmes OOD 
Diminution after combustion, ........ 73°5 
Carbonic acid gas, produced,........+. 1OL:O 
BeRGUG TAS 2: 95:0 weed vis = MARY sheen) 1 AEE, 
Bi ydrogenisrasi, 1/4 «iam nmin ns Gitte 49 cia SE 
Daring the combustion a quantity of ‘oxygen. disappears equal to 
about 1} of the vapour employed. The carbonic acid gas produced ' 
represents one voluine, and I suppose that the other fourth is em-= 
ployed in forming water ; for it is impossible to doubt that hydrogen 
enters into the composition of ‘prussic acid. From the laws of che- 
mical proportions, we may conclude that prussic vapour contains - 
just as much carbon. as will form its own bulk of carbonic acid, half 
a volume of azote, and half a volume of hydrogen. This result is 
evident for the carbon; and ‘though, instead of 50 azote and: 
hydrogen, which ought to be the numbers according to our suppo- 
sition, we obtain 46 for the first, and 55 forthe second. This is 
doubtless owing to a portion of the azote and oxygen having disap- 
peared, in order to form nitric acid. On this supposition we ought 
obviously to find too little azote and too much hydrogen, because 
the quantity of this last can only be judged of by the oxygen which’ 
has disappeared. But are the elements which I have pointed ‘out 
the only ones which enter into the composition of prussie acid? Are 
the proportions exact? We shall answer these questions by com- 
paring the density of prussic vapour to the sum of that of its ele- 
ments; and by attending to this, that since a volume of vapour 
RY pes a volume of carbonic acid gas, half a volume of azote, and _ 
alf a volume of hydrogen, the density of the vapour, if our analysis » 
be correct, ought to be equal to that of the vapour of ‘carbon, and 
to half that of azote and hydrogen. 
‘But the density of carbonic acid gas being 1°5196; and that. of } 
oxygen 1°1086, the density of the vapour of carbon is 1°5196° — 
11036 = 0°4160, , 
