1819.] Cyanogen and Hydrocyanic Acid. 439 
to 260 centimetres the total of the cyanogen for the 280 in the 
preceding experiment. 
In another experiment, in which only two decigrammes of 
sulphur for two grammes of cyadide of mercury were employed, 
145 centimetres of a gas were obtained, which did not blacken 
the solution of acetate of lead ; but which furnished sulphurous 
acid when burned. This result shows that cyanogen is capable 
of holding a little sulphur in solution. 
M. Vauquelin has observed that when the mixture of cyadide 
of mercury and sulphur begins to get hot, a kind of explosion 
takes place, occasioned by the sudden disengagement of a great 
quantity of gas, which carries with it into the neck of the retort, 
and even into the receiver, a portion of sulphate of mercury. 
The disengagement afterwards takes place more slowly. There 
remains in the retort a little sulphur, cinnabar, and some metal- 
lic mercury, which could not be converted into sulphuret, pro- 
bably in consequence of the great rapidity with which the gas 
was disengaged, carrying with ita little sulphur. M. Vauquelin 
never observed in the residue that charry matter which is 
always observed when cyadide of mercury is distilled alone. 
“ This experiment,” observes M. Vauquelin, “ proves that 
sulphur decomposes cyadide of mercury at a temperature much 
lower than that at which it is decomposed when alone. It 
appears to me that it would be possible in this way, by employ- 
ing the requisite proportion of sulphur, to obtain pure cyanogen, 
without any portion of it being decomposed.” 
On what happens during the Solution of Cyadide of Potash in 
Water. 
M. Vauquelin shows in this paragraph that whenever cyadide 
of potash is dissolved in water ammonia is formed. 
A mixture of equal parts of rasped horn and subcarbonate of 
potash calcined at a red heat till they underwent fusion, being 
dissolved in water, immediately evolved ammonia. This was 
easily shown by suspending over the vessel litmus paper reddened 
by an acid. It became speedily blue. This liquor being distil- 
led furnished a very alkaline liquid, which did not precipitate 
lime-water, nor form prussian blue with acid sulphate of iron. It 
was, therefore, pure ammonia. 
We ought not to omit mentioning that during the calcination 
of the mixture above-mentioned, particularly towards the end of 
the process, M. Vauquelin observed white vapours, which had 
a well-characterized odour of hydrocyanic acid. Does this acid 
exist quite formed in the fused matter? M. Vauquelin thinks 
otherwise. If it were present, the matter in dissolving would 
not produce ammonia. He conceives that the cyanogen while 
passing through the moist atmosphere to the organs of smell, is 
converted into hydrocyanic acid; the formation of which is 
