44 Materials for a History of the Prussiutes. 



the red oxide, and seems to take .a surcharge of it : for it 

 does not any longer crystallize in prisms, but in small 

 groups of very fine needle-like crystals. Their solutions 

 also require more concentration : new solutions do not re- 

 store them to their first form. 



This salt heated in a retort is very easily decomposed, and 

 indeed totally, if we be not too hasty in heating it. It 

 is sufficient to heat some grains of it in a tube three or four 

 lines in diameter closed at one end. If, while it is heated, 

 we present the open end to the flame, the prussic gas mixed 

 with gaseous oxide takes fife. Its flame is red and blue, 

 terminated by a vellowish aureola. One hundred grains of 

 prismatic prussiate distilled yielded 72 grains of mercury, 

 and on another occasion 72-£. 



The residue, being from eight to nine grains, was a mix- 

 ture of charcoal and carbonate of potash. This is not sur- 

 prising; the alkali cannot (it-compose the prussiate of mer- 

 cury : it certainly belongs to the Prussian blue, which was 

 that used in commerce. 



The products from this distillation are ammonia and oil 

 in abundance, besides a mixture of carbonic acid gas and 

 carbonic acid. 



There was apparently no prussiate with a base of oxide at 

 the i7iinimiim ; for the prussic acid, applied to mild mer- 

 cury, and to the nitrate with a minimum, base, eliminates a 

 portion of mercury, and gives prussiate with a base of red 

 oxide, the same as that obtained by treating this acid di- 

 rectly with red oxide. 



The red oxide also decomposes the simple prussiate. Po- 

 tass is also separated from it ; and as it has no action upon 

 the prussiate of mercury, the latter crystallizes in the mass. 

 It also completely decomposes the triple prussiate, which 

 requires long ebullitions : in this case the black oxide, 

 the clement of this salt, passes to the state of red oxide, 

 and is deposited in ochre. A part of the mercury gives up 

 to it the oxygen which it requires for this : hence it hap- 

 pens that we find it native with the ochre which is precipi- 

 tated ; but without the hyper-oxidation of the iron, which, 

 as we know, diminishes the affinities of this metal, the ox- 

 ide 

 / 



