432 M. Vauquelin’s Memoir on [Jung 
because its saturating affinity is much smaller than that of the 
potash or soda employed in the experiment. M. Vauquelin, 
from these facts, concludes, that the oxides are incapable of 
forming cyadides. 
Action of the red Oxide of Mercury on Cyanogen dissolved in 
Water. 
M. Vauquelin’s object in this experiment is to know if two 
salts are formed, and consequently two acids. 
For this purpose he put the peroxide of mercury in contact 
with cyanogen dissolved in water. The odour of this gas spee- 
dily disappeared, the volume of the oxide diminished, the liquor 
acquired a mercurial taste, and the residual mercury assumed a 
brownish tint. 
This liquor distilled in a retort gives a liquid charged with 
subcarbonate of ammonia, and there remain in the retort two 
salts which crystallize ; the one in square prisms, constituting 
cyadide of mercury; the other in square plates, sometimes 
bevelled on the edges, having a taste at first cooling and pun- 
gent, but afterwards mercurial. This salt is more soluble than 
cyadide of mercury, and flies off in smoke when thrown upon 
burning coals; while the cyadide of mercury decrepitates. 
Muriatic acid disengages from it a strong odour of hydrocyanic 
acid ; and if some time after we add a little potash to the mix- 
ture, a white precipitate falls, and ammonia is disengaged. In 
this case two salts have been formed, as happens with chlorine. 
But do these salts differ in the nature of their acid? or is there 
any other difference between them besides the existence of 
ammonia in one of them? Notwithstanding the probabilities in 
favour of the formation of two acids, M. Vauquelin does not 
venture to give an opinion, but leaves the point to be determined 
by future investigations. 
Action of Hydrocyanic Avid on Hydrate of Copper. 
The object of this investigation is to determine the difference 
between the simple and the triple prussiate. 
When hydrocyanic acid is placed in contact with oxide of 
copper, it immediately loses its odour, and forms a compound 
of a greenish-yellow colour, which crystallizes in small grains. 
If we wash this compound with boiling water before it crystal- 
lizes, it becomes white, and dissolves in ammonia without 
colouring it, provided always that it is not in contact with the 
atmosphere. This fact had been already observed by Scheele. 
This prussiate of copper dissolves with effervescence in nitric 
acid; and M. Vauquelin is of opinion that he recognized the 
odour of hydrocyanic ‘acid mixed with that ofnitrous gas. When 
placed in contact with caustic potash, it becomes yellow, then 
brown, and finally slate grey. 
When distilled in a tube, it gives in the first place an acid 
