HISTORY OF PRUSSIATES. 103 



•will not kindle of itself, if it be wetted with niiric acid of 

 40°, it burns with great vividness. I am inclined to think, 

 that in this combustion the iron burns in conjunction with 

 the charcoal. 



If the prussian blue were without alum, this residuum Residuum. 

 contains nothing but charcoal and iron. 



Muriatic acid disengages from it with the greatest facility Treated with 

 that aromatic hidrogen, which announces iron steelified, or muna lc aci .* 

 combined with carbon. The residuum is pure carbon, one 

 of the elements of the acid destroyed. As to the carbonic 

 acid and gaseous oxide, it is equally evident, that they are 

 the two oxidations of carbon, a maximum and minimum, 

 produced by the oxigen of the two oxides found in the 

 prussian blue. 



This decomposition is obtained by a heat so gentle, that Gaseous oxide 

 it appears to me a convenient mode of procuring the gaseous ° 

 oxide of carbon. As there is not the slightest appearance No appearance 

 of oil, it is somewhat surprising, that in the course of the 

 destruction of a compound in which carbon and hidrogen 

 abound, no part of these combustibles should be found to 

 present themselves under circumstances in which oil would 

 be formed. 



The oily and aromatic character, that the hidrogen as- Iron unites with 

 sumes during the solution of the residuum, demonstrates mo( j erate beau 

 likewise, that the combination of iron with carbon doe$ 

 not require a very high temperature. The charcoal of 

 blood, which is obtained by a very low heat, equally con* 

 tains iron in the state of carburet; for this likewise yields 

 odoriferous hidrogen with muriatic acid. I think I have 

 somewhere else observed, that Priestley was struck with 

 the bituminous smell of the hidrogen furnished by car- 

 buretted iron. 



Distillation of the Triple Prussiate of Potash. 

 This salt loses ten per cent of water, and with it its Destructive 

 colour, .for it becomes white ; but it does not begin to th g triple ° us . 

 soften till it is at a red heat. Some chemists have imagined, siatc ot'pota*h. 

 that roasting or melting it would afford the means of freeing 

 it from oxide, but the following results will show, that 

 Ihese processes lead to nothing useful. 



When 



