AND OF SALTS OF THE PEROXIDE OF IRON. 
257 
pure hydrogen gas for some length of time into the solution 
in question ; it appeared, however, to undergo no change 
whatever in its chemical constitution under these circum- 
stances. But when the hydrogen came into contact with 
the dissolved percyanide, either in a nascent state or in cer- 
tain chemical combinations, it had a different action. If two 
vessels, communicating with one another by means of a 
porous septum, for instance animal membrane, be filled with 
the dissolved cyanide, and the conducting wires of a some- 
what powerful battery be conveyed into the liquid of these 
vessels, a portion of the solution of the percyanide in which 
the negative electrode is immersed, i. e. in which hydrogen 
is separated, is rapidly changed, and affords a blue precipitate 
with pernitrate of iron. 
Hydrogen combined w T ith sulphur, selenium, phosphorus, 
arsenic, antimony and tellurium, although still gaseous in 
these combinations, acts nevertheless very rapidly on the 
solution of the ferridcyanide, and indeed in a similar manner 
to nascent hydrogen. If either one of the last-mentioned 
gases be passed for only a short time into the solution of the 
cyanide, it is so much altered by it that it affords blue pre- 
cipitates with persalts of iron, even after the expulsion of 
any gas dissolved in the liquid. If the solution of cyanide, 
before being submitted to the action of any of these hydrogen 
compounds, be mixed with a solution of the pernitrate of iron, 
a very considerable precipitation of prussian blue takes place 
on the entrance of the gas into the mixture. It must, how- 
ever, be observed that the three first mentioned gases act far 
more rapidly than the three metallic hydrogen compounds 
are capable of doing. 
If the solution of cyanide be allowed to stand with sether 
or alcohol for ever so long, it does not appear that the mixed 
substances act on one another under these circumstances, since 
a solution thus treated is not rendered perceptibly blue on the 
addition of a persalt of iron. But if, besides the aether or 
alcohol, some nitrate of iron be added to the dissolved cyan- 
23* 
