with the Prussiate of Potash. 213 



a solution of the prussiate of potash : the liquor gradually loses 

 its yellow tint, becomes of a dark greenish-yellow, and, when fully 

 saturated, of a deep brownish-red colour. From this solution the 

 salt is obtained in regular crystals, though with considerable dif- 

 ficulty, owing to its tendency to decompose, and to deposit a 

 green sediment. I have never been able by this process to pro- 

 cure crystals either so large or so permanent as those I got 

 at first from the Prussian blue. By another process, however, 

 which I shall presently describe, it may be formed with great 

 ease, and in beautiful crystals. 



GMELIN calls this salt a peculiar Cyanide of Iron and Potas- 

 sium (besonderes Cyan Eisen Kalium), and gives the following 

 as its composition : 



By Experiment. 



Potassium, = 35-873^ 



Iron, = 17 22 > 102-093 



Cyanogen, 49'0 ,) 



taking the mean of his results ; and from this he deduces, as its 

 atomic constitution, 



Potassium, 3 atoms, 117'6 35'89 per cent. 

 Iron, = 2 ... = 54-0 = 16'49 



Cyanogen, =6 ... 156-0 = 47'62 



1 atom, = 327-6 = 100-00 

 which, by correcting the atomic weights, becomes 



Potassium, 3 atoms, 15'0 = 120 = 36*1445 per cent. 

 Iron, 2 ... = 7-0 = 56 = 16-8674 



Cyanogen, 6 ... = 19'5 = 156 = 46'9879 



1 41-5 332 99'9 



