ELECTROLYSIS OF SECONDARY COMPOUNDS. 
9 
at the zincode. He observes. “ that one equivalent of the yellow ferrocyanate is de- 
composed, the free potash travels one way, and the hydroferrocyanic acid the 
other. The oxygen unites with the hydrogen of the acid and sets ferrocyanogen at 
liberty ; this again unites with an equivalent of the ferrocyanuret of potassium to 
form the f 'err oses quicyanuret." It is evident from this, that this gentleman enter- 
tains a very different notion of the steps of the electrolysis to that which we feel 
justified in supporting, and that therefore he has failed to place it in the point of view 
to which we propose to adhere. 
(/.) We commenced our inquiry by carefully repeating Mr. Smee’s experiment in 
a diaphragm cell, charged throughout with a strong solution of the yellow ferro- 
cyanide of potassium. A voltameter was included in the circuit, and the power of 
twenty cells of the small constant battery was employed. Gas was evolved at the 
platinode, which was tested and found to be pure hydrogen ; it was in equivalent 
proportion to the gases in the voltameter. No gas was at first evolved at the zincode, 
but the solution in that cell became gradually red, particularly at the surface. When 
4 inches of hydrogen had been collected at the platinode a slight disengagement 
of gas commenced at the zincode, which continued, and proved to be oxygen, and 
was in the proportion of one-third of the gas from the platinode. After 16 cubic 
inches had been collected from the platinode, we stopped the experiment and ex- 
amined the results. 
The platinode solution was much paler than before, and was alkaline. The zincode 
solution was deep green and acid, and the zincode plate was covered with a slight 
film of Prussian blue. Crystals of the red ferrocyanide separated from the zincode 
solution by spontaneous evaporation, and when the evaporation was complete, a radi- 
ated mass of a purplish-brown colour was obtained : on solution a small quantity of 
Prussian blue remained, and the solution had lost its acid reagency. The addition 
of acetate of lead to the solution produced but a scanty precipitate, proving the 
quantity of yellow ferrocyanide remaining in it to be but small. 
The explanation of these results is, we think, sufficiently obvious. Ferrocyanogen 
was doubtless transferred to the zincode, and potassium to the platinode, the former 
combined with a portion of the ferrocyanide to form the subsesquiferrocyanide ; the 
process being accelerated by the abstraction of a portion of the potassium passing 
over to the platinode, where by its reaction upon the water of the solution it was 
converted into potassa with the evolution of hydrogen. As the process proceeded 
more ferrocyanogen was given off at the zincode than could be absorbed by the yel- 
low salt ; and it consequently began to react upon the water, becoming converted by 
the abstraction of its hydrogen into hydroferrocyanic acid, its oxygen being evolved. 
The acid reaction is thus accounted for, as well as the deposition of Prussian blue, 
from the well-known spontaneous decomposition of the acid. 
(m.) This experiment was several times repeated with variation of the quantities, 
but with substantially the same results. The evolution of oxygen from the zincode 
MDCCCXLIV. 
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