350 Materials for a History of the Prussirites* 



with all its black oxide. This prussiate of manganese is 

 therefore also a combination tripled (trisulee) by the black 

 oxide : the prussiate of copper, which is of a blood-red co- 

 lour, is, without doubt, another combination of it, for the 

 simple prussiate of copper is yellow. 



Scheele assures us, that other oxides have also the pro- 

 perty of trebling (dc trisuler) the simple prussiate of potash. 

 It is a course of inquiry so much the more interesting, as it 

 is likely to lead to the discovery of some colour equally pre- 

 cious with that of Prussian blue : and lastly, we may con- 

 clude, from all wc have seen, that there exists no simple 

 prussiate of iron, a kind of combination of which other 

 meials are nevertheless susceptible, as we shall soon see. 



Distillation vf Prussian Blue. — This prussiate when ex- 

 posed to a high temperature is destroyed. It is replaced by 

 new products which confirm the theory given us by Ber- 

 thollet, upon the nature of the prussic acid. We obtain 

 acid which escapes its destruction, carbonate of ammonia, 

 a little free carbonic acid, and gaseous oxide in abundance : 

 one ounce of (lit blue of commerce of a good quality gave 

 a little more than two pints and a half of this gas ; what 

 was wanting to complete the three pints was carbonic acid. 

 The water of the tub contained prussic acid fixed by am- 

 monia. This prussiate follows, as we know, the traces of 

 that of simple potash : it cannot form blue with solutions ot 

 red oxide ; but it gives them with those of oxide at the mi- 

 nimum, because at the same moment it constitutes itself 

 triple or dyeing prussiate. 



The residue weighed five drachms 52 grains. It was per- 

 fectly black, and answered to the magnet : it is a pyrophorus 

 which rapidly takes fire. If, after having preserved it ill corked 

 so long that it cannot take fire of itself, we moisten it with 

 nitric acid at 40 degrees it burns in a very lively manner. 

 I am inclined to think that in this combustion the ircyi 

 burns jointlv with the charcoal. 



If Prussian blue has no alum in it, we find only charcoal 

 and iron in the residue. 



-The muriatic acid extricates from it with the greatest fa- 

 cility that aromatic hydrogen which announces iron com- 

 bined 



