160 
Selected Articles. 
ART. XXXVII. — ON THE REACTION WHICH TAKES PLACE WHE# 
FERROCYANURET OF POTASSIUM IS DISTILLED WITH DI- 
LUTE SULPHURIC ACID ; WITH SOME FACTS RELATIVE TO 
HYDROCYANIC ACID AND ITS PREPARATION OF UNIFORM 
STRENGTH. By Thomas Everjtt, Esq., Professor of Chemistry to the 
Medico. Botanical Society, &c. 
As the decomposition of the ferrocyanuret of potassium by 
means of sulphuric acid is likely to become the only method 
by which hydrocyanic acid will be prepared for chemical 
and medical purposes, on account of the cheap rate at which 
this salt is now to be had chemically pure ; and as in all ope- 
rations of this sort the more exactly we adhere to the pro- 
portions indicated by an accurate knowledge of the nature of 
the interchange which takes place during the process, the 
more uniform and satisfactory are the results, and the more 
do w r e economize our time, 1 have been induced to examine 
very narrowly the above reaction. 
(2 ) Assuming the composition of the crystallized yellow 
ferrocyanuret of potassium to be 2 K Cy + Fe Cy + 3 Aqi 
I find that on boiling it with sulphuric acid in a close vessel, 
fths of the potassium remain in solution as bisulphate of po- 
tassa, its cyanogen going off as hydrocyanic acid : the re- 
maining ^th combines as cyanuret of potassium with all the J 
cyanuret of iron to form a yellow insoluble salt: thus, 
2 proportions 
oi the 
crystals. 
with 
5 4 K 
}4Cy 
5 2 Fe 
6 s 
}2Cy 
6 Aq 
3 Cy H. which escape as gas. 
3 (k + 2 s ) bisulphate of potassa in solution. 
3 Aq — free. 
K Cy+2 Fe Cy, which fall as yellow salt. 
Or In numbers : 
2 proportions of salt 
39.15 X 4 potassium 
28 X 2 iron 
26.39 x 6 cyanogen 
9x6 water 
Real 
sulphuric 
acid. 
40x6 
Results. 
3 (26.39 + 1) hydrocyanic acid, 
3 (39.15 + 8)4-6 (40) bisulphate of potassa. 
9x3 free water. 
(39.15 +26.39) + 2 (28+26.39) yellow salt. 
