290 ON PRUSSIAN BLUE 



prove this, I distilled a mixture of six parts of manganese, 

 finely powdered, and one part of pulverised Prussian blue, 

 and I obtained in the receiver nothing but aerated volatile 

 alkali, without the least mark of colouring matter. 



It may be observed, (1) That it is probable that this 

 matter may be made to assume aerial form, though I have 

 hitherto not been able to effect this. 



(2) It is remarkable that our colouring matter, after it 

 has united with the alkali, or with the lime, forms a men- 

 struum, capable not only of dissolving metallic calxes, but 

 also of constituting a triple salt, which is not decomposed by 

 the aerial acid, as happens with the lixivium sanguinis and 

 the precipitating liquor, when exposed to the free access of 

 air. Iron is not the only metal which has the property of 

 fixing the colouring matter (Sec. ir. (c)), the same quality 

 belongs likewise to gold, silver, copper, and probably to 

 several other metallic calxes ; for if, after these calxes have 

 been precipitated, a sufficient quantity of precipitating liquor 

 be added, in order to redissolve them, the solution remains 

 clear in the open air, and in this state the aerial acid does 

 not precipitate the metallic calx. 



(3) It is another remarkable circumstance that, except 

 nitrated silver, nitrated mercury, and aerated calxes (Sec. 

 xn. (a)), this matter does not decompose metallic solutions 

 by a single elective attraction. Now, as we know that 

 Prussian blue is not soluble in acids, it naturally follows 

 that the colouring matter has a greater affinity with iron than 

 acids have, notwithstanding there is no precipitation per- 

 ceived when this matter is mixed with the solution of vitriol 

 of iron. It may not be an easy matter to give a satisfactoiy 

 explication of this phenomenon. 



