156 
Book II. 
ACIDS. 
prussic acid does not contain ammonia ready formed; but 
that it is a triple compound of carbon, hydrogen, and 
azot, in proportions which he was not able to ascertain. 
This conclusion has been still farther verified by Mr 
Clouet, who found that when ammoniacal gas is made 
to pass through a red hot porcelain tube containing 
charcoal, a quantity of prussic acid is formed*. This 
experiment does not succeed unless a pretty strong heat 
be applied to the tube †. 
Fourcroy and several other chemists believe, that the 
prussic acid contains also a portion of oxygen in its 
composition, resting chiefly upon an experiment of 
Vauquelin f. This is certainly possible, though it has 
not been proved; and the experiments of Berthollet 
render it somewhat unlikely. 
* Ann. de Cbim. xi. 30. 
Jour. de l'Ecole Polytechn. I. iii. 436. 
Vauquelin's experiments were as follows : 
ExPER. I. Put into a retort 100 parts of the muriat of ammonia, 50 
parts of lime, and 25 parts of charcoal in fine powder ; adapt to the re 
tort a receiver containing a slight solution of the sulphat of iron, and im 
merse into it the beak of the retort ; then apply a brisk heat, and conti 
nue the action of the fire until nothing more is disengaged. 
ExPER. II. Put into a retort 100 parts of the muriat of ammonia, 50 
parts of semi-vitreous oxide of lead, and 25 parts of charcoal; adapt a re 
ceiver containing a solution of sulphat of iron, and proceed as before. 
Stir well the liquors contained in the receivers, and expose them to the 
air for several days, in order that the combination between the oxide of 
iron and the prussic acid may be perfect, and that the prussiat of iron 
may absorb as much oxygen as is necessary for its passing to the state of 
blue prussiat, and for its being proof against acids : then pour into these 
liquors equal quantities of sulphuric acid well diluted with water, and 
you will have prussian blue, the quantities of which will be as one to six; 
that is to say, the prussian blue of the experiment in which Vauquelin 
employed oxide of lead, was six times more abundant than that of the ex 
periment in which he employed only lime to disengage the ammonia,