HISTORY OF PRTJSSIATES. Q^Q 



because the charcoal of blood lias not iron sufficient to con- part of thetri- 

 vert all the simple prussiate that is formed during the calci- J 1 ^™^ 6 

 nation into a tiiple salt, or that part of this salt is again 

 reduced to the state of simple prussiate by the loss of part 

 of its oxide, as we have seen takes place when it is heated 

 alone. Of these two opinions, however, I should be in- 

 clined to adopt the latter, because I have observed, that the 

 ashes of the charcoal that has been lixiviated always afford 

 a great deal of iron : we have no reason, therefore, to sup- 

 pose, that in calcining the carbonaceous alkaline mixture 

 iron is wanting to the prussiate; and indeed, if we reflect 

 on the subject, it is surprising, that the triple prussiate, 

 %vhich actually exists in the lixiviums, should have been ca- 

 pable of defending its oxide against the effects of the car- 

 bon continually tending to reduce it. The whole of this, 

 however, is at present very obscure : we neither know the 

 period when the prussic acid is formed, whether it be de- 

 stroyed to be again reproduced, nor, lastly, the degree of '"■ 

 heat required to obtain the greatest possible quantity of 

 either of the prussiates, that are the objects of the manu- 

 facturer. 



The existence of the triple prussiate in the lixivia may be Proof that the 

 demonstrated by the following - experiment. hx'ma contain 



_ t ■ • • i it- • i mi triple prussiate 



Saturate a lixivium with aqueous sulphuric acid. The 



carbonic acid first flies off, and next the prussic acid of the 

 free prussiate. After this, heat must be applied, when the 

 triple prussiate is attacked, and the white prussiate of iron 

 is made apparent. Beside this, concentrated lixivia long 

 kept deposit octaedral crystals of triple prussiate. 



The prussic lixivium has two very distinct tastes; one of Their quality 

 potash, the other of kernels. By the latter we may judge at ma y be judged 

 once of its quality. If it affect the palate but slightly, the ta s te# 

 lixivium is defective, either because the mixture was insuffici- 

 ently heated, or the animal charcoal in too sparing proportion. 

 I am of opinion too, that the calcination of the mixture in the 

 open air does not contribute to the augmentation of the 

 prussiate ; and that it would probably be more advantageous, 

 and save trouble, to heat it in covered crucibles in a reverbe- 

 ratory furnace, since it has been proved, that stirring the 

 mixture is not necessary to the success of the operation. 



When 



