Royal Institute of France. 311 
ROYAL INSTITUTE OF FRANCE. 
Analysis of the Lalbours of the Class of Mathematical and 
Physical Sciences for the Year 1815. By M, Cuvier. 
CHEMISTRY. 
We have during the last two years spoken of those acids with- 
out oxygen, or, as they are now called, hydracids, which have 
made such a considerable breach in the imposing edifice of the 
chemical theory of Lavoisier, ‘The labours of M. Gay-Lussae 
have this year proved that there is one more to add to this class: 
that which M. De Morveau had called prussic acid, because it 
enters into the composition of Prussian blue, and because, its ra- 
dical not being known, it was not possible then to derive from 
that source its denomination. 
The experiments of Margraaf, Bergman, and Scheele, did not 
admit of a doubt that in Prussian blue the iron was united with 
a substance which performed the part of an acid. M. Berthol- 
let had suspected however for a long time that oxygen did not 
enter into its composition, but merely carbon, azote and hydro- 
gen; and this suspicion has been changed into a certainty by 
Gay-Lussae. 
On decomposing, with the precautions which he points out, 
the prussiate of mercury by the hydrochloric (otherwise muriatic) 
acid, he obtained pure prussic acid ; and we have already 
spoken in one of our preceding reports of the singular properties 
which he found in it in this state, and chiefly of its extreme vo- 
latility. On afterwards burning the vapour of this acid by 
oxygen and the electric spark, he obtained determinate quan- 
tities of water, carbonic acid and azote. The oxygen consumed 
in the production of the two first of these substances is wanting ; 
and it follows from this conclusion, that oue volume of vapour 
of prussie acid results from the combination aud concentration 
of one volume of vapour of carbon, half a volume of azote, and 
half a volume of hydrogen; or, by expressing these volumes by 
weights, according to the density of each of these vapours, 100 
parts of acid contain 44°39 carbon 
51:71 azote 
3°99 hydrogen. 
Thus the prussie acid contains more azote and less hydrogen 
than the other animal substances, from which it is particularly - 
distinguished by ¢he total absence of oxygen. per 
This is the first hydracid known, the radical of which is dey 
eomposable; and this radical M. Gay-Lussac also succeeded in 
obtaining freed from its hydrogen. Not being able to preserve 
this epithet of prussic, which belongs only to an accident, he has 
given it the appellation of eyanogene (that is to say, producing’ 
blue), The prussic acid will therefore take in future the deno- 
U4 mination 
