5 1 G Chemical Society. 



parts of peailashes and animal matter, or ten parts of tlie former 

 and eight parts of carbonized animal matter. Tliree or four per 

 cent, of iron filings are usually added to the mixture. After each 

 addition of animal matter the heat is urged until the whole is fused, 

 and the melted material, which is of a thick consistence, is not re- 

 moved from the pot until the charcoal is seen to be equally diffused 

 through the Mhole mass. The mass, after cooling, is placed in an 

 iron pan filled with water, the clear liquid after a time drawn off, 

 and water boiled several times on the insoluble residue. The liquids 

 are evaporated for crystallizing the salt at a temperature not exceed- 

 ing 203'^ Fahr. The formation of prussiate takes place after the 

 solution of the melted mass, by the action of the matters dissolved 

 upon the insoluble residue ; for this melted mass yields nothing but 

 cyanide of potassium to alcohol, and contains no prussiate. In ex- 

 planation of the formation of cyanide of potassium in the melted 

 mass, it is stated that metallic potassium readily produces that salt 

 when fused with calcined blood, disengaging at the same time a 

 considerable quantity of charcoal ; the proportion of nitrogen to 

 carbon, in cyanogen, being one equivalent of the first to two of the 

 last, while in blood, hair, and horn, the proportion is 1 to 6. Now 

 when these animal matters are fused at a high temperature with 

 potash, the free charcoal reduces the potash to the state of potas- 

 sium ; the latter then acts upon the azotized carbonaceous matter, 

 forming cyanogen, with which it unites. A second mode in which 

 cyanide of potassium is produced, is when ammoniacal gas is con- 

 ducted over a mixture of carbonate of potash and charcoal at a red 

 heat. This is accounted for by the action of ammonia upon char- 

 coal alone at a red heat ; the gas is entirely converted into hydro- 

 cyanic acid and hydrogen (N H3 and 2C = H, N C.j and 2H). 

 Now hydrocyanic acid decomposes carbonate of potash at a red 

 heat, forming cyanide of potassium. Hence the product of cyanide 

 of potassium is most considerable when the animal matter is used in 

 its natural state, and not previously carbonized, a fact of which the 

 manufacturers of prussiate of potash have long been aware from 

 experience. To account for the subsequent conversion of the 

 cyanide of potassium in the process into prussiate, it is abso- 

 lutely necessary that iron exist in the lused mass ; but it may 

 indifferently be in the condition of metallic iron, the protosulphuret 

 or the protoxide of iron. The first is readily dissolved by a 

 solution of cyanide of potassium with evolution of hydrogen gas 

 (3K Cy with H O and Fe = 2K Cy, Fe Cy and K O and H) ; the 

 second witli the formation of sulphuret of potassium, and the third 

 with that of caustic potash. When the iron is added in the state of 

 protosulphate to a solution of cyanide of potassium, one-third of the 

 latter salt becomes cyanide of iron (a brown insoluble matter), 

 which is dissolved by the other two-thirds of the alkaline cyanide, 

 and the ferrocyanide formed. These processes are not altered in 

 the slightest degree by mixing caustic potash or its carbonate, or 

 the sulphuret of potassium, with the solution of cyanide of potas- 

 sium. Much of tlie iron necessarv, it is well known, is derived from 



