1819.} Cyanogen and Hydrocyanic Acid. 431 
in suspension a brown matter in very minute particles. Allowed 
to become clear by repose and evaporated cautiously, it yields 
crystals which have a cooling and pungent taste, which swell 
and evaporate in smoke, leaving a slight trace of charcoal when 
thrown upon a red hot iron, but do not inflame. 
They exhibit quite different phenomena from those ofa nitrate 
when thrown upon red-hot charcoal. The aqueous solution of 
these crystals precipitates the nitrate of silver and acetate of lead 
in white flocks soluble in nitric acid. It occasions a slight mud- 
diness in the solution of nitrate of barytes, which disappears on 
the addition of nitric acid. It gives out a strong odour of 
ammonia when triturated with caustic potash, and does not 
furnish prussian blue by means of sulphate of iron, not even 
after being mixed with potash. However, the addition of weak 
muriatic acid developes in it a strong odour of hydrocyanic acid, 
which cannot be deceitful, says M. Vauquelin, for a paper on 
which oxide of iron had been deposited being exposed for some 
time to this vapour, became blue when plunged into weak sul- 
phuric acid. 
' It is evident from these facts that the crystals in question have 
ammonia for their base. But what is the acid which forms their 
other constituent? Vauquelin is of opinion that it must be a 
new acid hitherto unknown. ‘The small quantity of these crys- 
tals which this celebrated chemist obtained did not put it in his 
power to separate this acid and to study its properties. 
From the preceding facts, we may conclude that the decompo- 
sition of cyanogen dissolved in water occasions the formation of 
three new acids and of ammonia, which saturates them. One of 
these is hydrocyanic acid, and the two others are carbonic acid 
and the peculiar oxygenized acid just mentioned, to which 
M. Vauquelin has given the name of cyanic acid. 
The brown matter deposited is owing to this, that the quantity 
of hydrogen requisite to produce hydrocyanic acid and ammonia 
does not produce a sufficient quantity of oxygen to convert all 
the carbon and azote of the cyanogen into an acid. 
Way in which Cyanogen acts on the Metallic Oxides. 
M. Vauquelin explains in this paragraph the general way in 
which cyanogen acts on the oxides. 
This action is not the same with regard to all the oxides ; but 
the differences have not been exactly appreciated. The alkaline 
oxides act with great energy on cyanogen. They make it 
undergo a decomposition absolutely similar to that observed with 
water alone ; with this difference, however, that the alkalies act 
much more rapidly. The brown matter appears all of a sudden’; 
but it ceases to be evident when there is an excess of alkali, 
because this last substance has the property of dissolving it. 
There are formed likewise in this case the three acids formerly 
pointed out, and ammonia; but this last substance is disengaged, 
