438 M. Vauquelin’s Memoir on (Jung, 
sulphuret appeared till caustic potash was added ; and the super- 
natant liquid formed a prussian blue when mixed with acid 
sulphate of iron. But this same hquor, which had no action on 
nitrate of lead, precipitated abundantly nitrate of silver and 
muriate of gold. In the last case only, the cyanogen did not 
become sensible. 
What ought we to think of this liquor? asks M. Vauquelin. 
Is it merely a combination of cyanogen and sulphuretted hydro- 
gen? The facts stated seem inconsistent with this opinion. Is 
it hydrocyanic acid holding sulphur in solution proceeding from 
a reciprocal decomposition of the two gases? This opinion 
appears more probable to M. Vauquelin. But were it true, how, 
he asks, is the smell of sulphur not perceptible? And how can 
we explain the reproduction of sulphuretted hydrogen and of 
cyanogen :by the solution of lead to which potash is added? 
This difficulty is not easily got over. To throw ‘some light upon 
the subject, ‘s put hydrocyanic acid in contact with sulphur in a 
state of minute division ; but the two bodies did not act sensibly 
on each other. But he does not consider this negative experi- 
ment as sufficient to overturn the preceding opinion ; because 
the sulphur, however minutely divided, can never be ina state 
comparable to what it is in when thrown down from sulphuretted 
hydrogen gas. This liquor, whatever explanation be given ofits 
composition, is very remarkable, from its neutral state. The 
class of acids has not hitherto presented any analogous com- 
pounds. 
Action of the Oxide of Mercury on Triple Prussiate of Potash. 
M. Vauquelin proves that by this operation a quadruple salt is 
formed. 
The cyadide of mercury, placed in contact with potash, does 
not undergo any sensible change. But the case is different 
when the ferrugmous prussiate of potash is placed in contact 
with the red oxide of mercury. There is precipitated a ferrugi- 
nous deposit of subhydrocyanate of iron, and a part of the potash 
is separated, the oxide of mercury combining instead of it with 
the hydrocyanic acid. The new quadruple salt resulting from 
this smgular action has properties peculiar to itself. 
Action of Sulphur on Cyadide of Mercury. 
M. Vauquelin endeavours to discover by this action the rela- 
tive affinity of sulphur and cyanogen. 
Two grammes of sulphur and as much cyadide of mercury, 
mixed accurately together and distilled, furnished 280 cubic 
centimetres of a gas, which blackened the solution of acetate of 
lead, and formed sulphurous acid when burned ; results which 
demonstrate the presence of sulphuretted hydrogen in this gas. 
Analysis has proved to M. Vauquelin that 110 cubic centi- 
metres of this gas contained eight of foreign gas. This reduces 
