Mr. R. Phillips on the Triple Prussiate of Potash. 113 



According to M. Robiquet *, ferrocyanic acid is equivalent 

 to hydrocyanic acid and cyanide of iron, which would give as 

 its composition 



2 atoms cyanogen 52 



1 atom hydrogen 1 



i iron 28 



81 



Or, 4 atoms carbon 24- 



2 azote 28 



1 atom hydrogen 1 



1 iron 28 



81 

 Dr. Uref is, I believe, the chemist who last paid attention 

 to the composition of ferrocyanic acid : he states the compo- 

 sition to be 



Carbon 36-82 



Azote 35-29 



Iron 27-89 



100- 



This analysis differs considerably from all the preceding, not 

 only in the proportion of the elements, but also in the absence 

 of hydrogen: but Dr. Ure allows that he is unable to reduce 

 the results of his experiments to the atomic theory. 



Although Berzelius does not admit the existence of such an 

 acid as the ferrocyanic in his paper, contained in the Amiales 

 de Chimie et de Physique, already quoted, yet in a late work 

 ex\i\i\ei\ Chimie du Per (x>. 181.) he says that ferruginous hy- 

 drocyanic acid [Vacide hydrocyaniqiie ferruginc) is composed 

 either of 46-57 parts of prussic acid and 53-43 parts of prus- 

 siate of protoxide of iron, or of 46-57 of prussic acid, 45-77 of 

 cyanide of iron, and 7-66 of water. Adopting the former of 

 these views, let us examine whether it will not serve to clear 

 up the difficulty which exists not only as to the composition 

 of ferrocyanic acid, but also as to the nature of the triple 

 prussiate of potash. 



I consider it as proved by Berzelius that the triple prus- 

 siate of potash after it has been moderately heated is in fact a 

 cyanide of iron and potassium; and it must I think in one case, 

 and perhaps in several instances, happen that the metals are 

 converted into oxides : this may be the case, as already no- 

 ticed by Berzelius, when the salt is in the state of crystals; the 



• Amuilet (le Chimie et de Physique, tom. xii. p. 294. 

 t Phil. Trans. 1823. p. 480. 

 Neva Series. Vol. 1. No. 2. Feb. 1827. Q water 



