162 
* Selected Articles, 
precipitated by nitrate of barytes, which proved that all the 
-sulphuric acid was in the solution. 
ifi.) The hydrocyanic acid given off was estimated by taking 
106.3 grs. of the ferrocyanuret of potassium in two fluid ounces 
of water, + (300 grains of dilute sulphuric acid of specific 
gravity 1.179) = 60 grains of real acid, and by means of a 
tube and cork conducting the vapour into a large receiver, 
containing a dilute solution of nitrate of silver : the cyanide 
collected and weighed, gave in 
Exp. No. 1, 103 grs.; No. 2, 102.3 grs.; No. 3, 101.4 gr. 
The calculated number is 100.8 grains. Most likely in ex- 
periment No. 1, the matter was not perfectly dried; but the 
three come sufficiently near to leave no doubt of the theoreti- 
cal quantity. 
(4) Hence 1 conceive that the exposition of the reaction 
given at the commencement of this paper is fully proved. I 
am well aware that in the 46th volume of the Annales de 
Chimie el de Physique, p. 77, M. Gay Lussac states that a 
white salt is produced during this reaction. I have operated 
with distilled sulphuric acid, conducted the process in a nar- 
row-necked flask, into which a stream of carbonic acid passed 
during the whole of the boiling, and it was always of a light 
lemon colour : in ordinary cases, when this extreme care was 
not taken, it was greenish. Perhaps M. Gay Lussac poured 
strong sulphuric acid on the powdered crystals, when a very 
complicated change takes place. (See Thomson, 7th edition, 
vol. ii. p. 251.) M. Gay Lussac also states, that after making 
a few experiments on the new salt, the results appear ("sem- 
blent" showing that he trusted more to the pen than the ba- 
lance,) to lead to the consequence that it is a compound of 9 
cyanogen, 7 iron, and 2 potassium, so that supposing we 
have enough of the original ferrocyanuret of potassium to 
yield 14 proportions of potassium, 7 of iron, and 21 of cyano- 
gen, then by boiling with sulphuric acid, 7 proportions of 
iron, + 2 potassium + 9 cyanogen fall, 12 of cyanogen go 
off as hydrocyanic acid, and 12 of potassium are dissolved 
by the sulphuric acid. Now, I prove by (b.) that the relation 
of the potassium dissolved by the sulphuric acid to that pre- 
