S54 Experiments’ on” Priissic Acid. [M. AY, 
and after’ being left some time in contact with the muriate of lime, - 
it may be finally driven into the receiver. . I usually employ con- 
cehtrated muriatic acid, and smaller in quantity than would be. 
necessary to decompose the whole of the prussiate of mercury, and_ 
I reserve the residue to obtain an aqueous solution of prussic acid by” 
adding. a new quantity of muriatic acid. a 
‘Prussic acid, obtained by the method just described, possesses the 
following properties. Jt is-a colourless liquid, having.a strong” 
smell, a taste at first cooling, then hot, asthenic ina high degree, 
and a true poison. Its specific gravity at 444° is 0'70583; at 64°, 
it is 0°6969, It boils at 814°, and congeals at about 3°. It then” 
crystallizes regularly, and affects sometimes the fibrous form ‘of 
nitrate of ammonia. The cold which it produces when reduced into 
vapour, even at the température of 68°, is sufficient to congeal it. 
This phenomenon is easily produced by putting a small drop at the 
end of aslip of paper or a glass tube. Though I rectified it re- 
péatedly on pounded marble, it retained the property of feebly red- 
dening paper tinged blue with litmus. The red colour disappeared 
as the acid evaporated. 
The ‘specific gravity of its vapour compared to that of air is 
0'9476.. This is the mean of two experiments, differing but little 
from each other. I ascertained it by the method formerly described. 
By calculations founded on its composition, and the condensation” 
of its elements, I obtained for its specific gravity only 0°9360, which 
is less than the preceding number by about a hundredth part. I 
think, however, that this last number should be preferred 5 for the 
difference between the two may be ascribed in part to errors in the © 
experiment. This small density of the vapour of prussic acid, com- 
pared with its great volatility, furnishes a new proof that the density — 
of vapours does not’ depend upon the boiling point of the liquids that _ 
furnish them, but upon their particular nature. 
To appreciate the better the effects of prussic acid on other bodies, 
I ‘began by determining ‘exactly the nature and proportions of its 
elements: his acid ‘being ‘very volatile, I took advantage of the — 
hot days of the month of August to analyze it in the eudiometer of 
Volta. My method was as follows. 
‘I filled a glass jar about two-thirds with oxygen gas over a mer- ' 
 curial trough at ihe temperature of between 86° and 95°, and then — 
filled it completely with the ‘vapour of prussic acid. When the — 
temperature of the mercury is reduced to that of the ambient air, 
I take a determinate volume of the gaseous mixture, and wash it in 
a solution “of potash. The residue, compared with the absorption 
which has taken place, gives’ exactly the ratio of the oxygen to the - 
prussic vapour. I can then employ this gaseous mixture without fear- 
ing that the prussie acid will condense, provided the temperature be 
not too'‘low; but during my experiments ‘it was never under 714°. I 
introduce a known volume into Volta’s eudiometer, ‘all the wires of 
whieh are of platinum; andl pass an electric spark-through it. ‘The’ 
combustion is very lively, and of a bluish-white colour. A white™ 
2? 
“a 
