THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



— ♦ — 



[THIRD SERIES.] 



APRIL 1842. 



XXXIX. On the Preparation of Cyanide of Potassium, and 

 on its Applications. By Prof. Liebig. Translated by Mr. 

 W.Francis, and communicated through him by the Author*. 



/^NE of the best methods of preparing the cyanide of po- 

 ^^ tassiiim is founded on the decomposition of the yellow 

 prussiate of potash at a red heat ; it is, however, attended 

 with much inconvenience, and a third part of the cyanogen 

 contained in the salt is lost. Considered as a compound of 

 two atoms of cyanide of potassium with one atom of pi'oto- 

 cyanide of iron, the former undergoes no change on exposure 

 to a red heat, while the latter is decomposed into carburetted 

 iron with evolution of nitrogen gas. The carburet of iron, 

 liite a sponge, imbibes the fused cyanide of potassium, to ob- 

 tain which Tree from iron and without loss a solvent such as 

 alcohol is I'equired. As the cyanide of potassium is possessed 

 of properties which render it highly valuable as a means of 

 reduction and separation in chemical analysis, I have endea- 

 voured to simplify the preparation of it. When eight parts 

 of the yellow prussiate are sharply dried (slightly roasted) on 

 a hot plate of iron, then finely powdered and mixed well with 

 three parts of dry carbonate of potash, and thrown at once 

 into a Hessian crucible previously heated to redness, and kept 

 at that temperature, the mixture fuses into a brown magma 

 with a lively evolution of gas. After a few minutes, when the 

 fluid mass has become red-hot, its dark colour is seen to be- 

 come brighter, and on continued fusion the salt becomes clear 

 and of ati amber-yellow tint. If from time to time a hot glass 

 rod be immersed in it, the adliering mass on cooling is at first 

 brown, afterwards yellow, and at last, towards the close of 



• Read before the Chemical Society, March 1, 1842. 

 Phil. Ma^ S. 3. Vol. 20. No. 1 31 . April 1 84-2. T 



