1821.] the Composition of Prussiates 447 



phenomena differing from those which have been hitherto 

 admitted. 



I have examined some of them with this view, and I think 

 that I can draw conclusions from my experiments regarding the 

 whole class of cyanurets. 



1. Cyanuret of Iron and Potassium. — I heated this in a small 

 apparatus, so arranged as to collect the gases evolved. At a 

 heat near redness, it melts ; and before this, it gives nothing 

 volatile or gaseous. But at a strong red heat, it is filled with 

 small bubbles which are disengaged at long intervals, and it 

 remains in this state, even at a temperature at which the glass 

 softens. While cooling, it has a deep-yellow colour ; but it 

 becomes almost colourless upon cooling to the temperature of 

 the atmosphere. Dissolved in water, it leaves a small quantity 

 of quadricarburet of iron in black flakes, and the solution has 

 alkaline properties and smells of hydrocyanic acid. The gas 

 obtained possessed all the characters of azote. The cyanuret of 

 potash separated from cyanuret of iron thus decomposed gives 

 hydrocyanate of potash with water, from whence its alkaUne 

 property and hydrocyanic odour are derived. 



2. Cyanuret of Iron and Barium treated in the same manner 

 is more easily decomposed at a red heat, gives abundance of 

 azotic gas, and leaves a residuum of cyanuret of barium and 

 quadricarburet of iron. The decomposition is usually so com- 

 plete, that the solution gives no blue with solutions of deutoxide 

 of iron ; but there are obtained a solution of a fine purple-red 

 colour, and a red precipitate. This red compound was first 

 observed by M. Vauquelin : he obtained it by treating deutoxide 

 of iron by hydrocyanic acid. That which was obtained in the 

 manner now described was not decomposed by ammonia ; and 

 after being evaporated to dryness, it was again partly soluble in 

 water. Another part appeared to be decomposed, and was 

 changed into a greenish mass. 



3. Cyanuret of Iron and Calcium is still more easily decom- 

 posed than that of barium. As it retains more water relatively 

 to its volume, it gives small drops of water, and a little carbonate 

 and hydrocyanate of ammonia. Towards the end, and when the 

 heat becomes red, it burns, but not vividly, in the same manner 

 as before observed, with respect to the hydrocyanate of iron and 

 ammonia. 



4. Cyanuret of Iron and Lead. — If it contains \^ ater, hydro- 

 cyanate of ammonia is obtained, which readily decomposes, and 

 becomes brown. At a red heat, it begins to evolve azotic gas, 

 and gives nothing else. When the disengagement of gas is 

 finished, if the retort be put in the middle of the fire, vivid com- 

 bustion is produced. If this temperature be employed before 

 the cyanuret is decomposed, the disengagement of azotic gas 

 occurs with such rapidity during the combustion, that a portion, 

 of the coaly mass is carried up with it. If all the water has 



