Efisaij upon the Compounds of Chjanogcn. 3 31 



Cyanogen, - _ - 52=2 atoms. 



Iron, - - - 28 = 1 " 



Hydrogen, - - - 1 = 1 '= 



81 representative numb. 

 Or supposing the cyanogen to be equally divided between the iron 

 and the hydrogen, we have 



Cyanuret of iron, - - 54=1 atom. 



Hydro-cyanic acid, - - 27=: 1 " 



But since it resembles in many of its properties the hydracids, it may 

 I think be regarded with propriety as a compound of bi-cyanuret of 

 iron (ferro-cyanogen ?) and hydrogen. 



Ferro-cyanogen, < ^ -J "^*= "' > 80=1 atom. 

 Hydrogen, - - - 1 = 1 " 



81 representative number. 

 Fcrro-cyanate of potassa. — ^When the hydro-cyanate of potassa, 

 which as before mentioned is strongly alkaline, is placed in contact 

 with protoxide of iron, a portion of the latter substance is dissolved ; 

 the solution acquires a yellowish tinge, and though still exhibiting an 

 alkaline reaction, may be now rendered neutral by the addition of 

 hydro-cyanic acid. The filtered solution yields, by evaporation, 

 crystals of ferro-cyanate of potassa. This salt is however most fre- 

 quently obtained in the laboratory by the decomposition of prussian 

 blue by a boiling solution of caustic potassa. It is obtained in the 

 form of quadrangular crystals of a lemon color ; it is destitute of odor, 

 and has a peculiar but not very unpleasant taste. When exposed to 

 a temperature a little below redness it gives off 13 per cent, of water, 

 and if the heat be much elevated and continued with access of air, 

 it is further decomposed, cyanuret of potassium being one of the 

 products. No change is produced in its solution by the addition of 

 the alkalies, of sulphuretted hydrogen, of the alkaline hydro-sulphu- 

 rets, or of tincture of galls; a fact which affords at least presump- 

 tive evidence that the iron it contains does not exist in the state of 

 oxide. Dilute muriatic and sulphuric acids when boiled with it pro- 

 duce an evolution of hydro-cyanic acid, with a precipitation of a 

 white substance, which is probably a proto-ferro-cyanate of iron. 

 When submitted to the agency of voltaic electricity, ferro-cyanic 

 acid appears at the positive, and potassa at the negative pole. It 

 consists of 



