46 Materials for a History of the Prussiates. 



with that of ammonia, were the latter present, does not 

 undergo the least change. 



Prussic Gas. — Twenty drachms of triple prussiate heated 

 in a.retort with a sufficient quantity of weak sulphuric acid, 

 charged four ounces of alcohol with about twenty -four 

 grains. I kept flic alcohol in a bell glass over the bath of 

 mercury: the gas is dissolved rapidly, but it would have 

 taken much more. The water of the intermediate receiver 

 was also surcharged with it : the smell was pungent and 

 suffocating, and its taste very strong of almond kernel. This 

 water did not disturb barytcs. The gas always tends to se- 

 parate from it, and continually elevates the stopper : if we 

 plunge a small matrass of it into hot water, it is rapidly se- 

 parated, and burns at the opening of it : if we bring the flame 

 of a candle to it, \\e perceive smoke; doubtless because a 

 part of the carbon escapes, as in the combustion of the vo- 

 latile oils. 



The prussic acid dissolved in water and well corked is de- 

 composed by itself. It is coloured yellow in four or five 

 months. It loses its smell gradually, becomes turbid, and 

 deposits a sediment of a coffee colour, which, after having 

 been heated, presents all the characters of carbon. 



It gives by distillation a little water, with prussic and 

 ammoniacal acid. The carbon is azotized ; and it has 

 resumed one of the principles which the acid abandons by 

 its destruction ; for I have heated it with carbonate of pot- 

 ash, and it gave me a lixivium proper for making Prussian 

 blue. 



But while the carbon is separated by retaining azote, the 

 greatest part of this last, added to the hydrogen, is consti- 

 tuted in ammonia : we also find it in the yellow liquor, with 

 the rest of the acid which has escaped its destruction. 



The prussic gas, dissolved in water, does not disturb the 

 solution of green sulphate: but when it has passed through 

 the changes we are about to mention, it disturbs it and gives 

 a blue, because the ammonia of new formation concurs to it. 

 Lastly, this liquor when distilled gives prussiate of am- 

 monia, and there is no longer any thing in it but atoms of 

 a charry matter which are deposited. It would have been 



important 



