TRANSACTIONS OF THE SECTIONS. 
53 
more especially on the comparative quantities of the substances em¬ 
ployed, a few experiments are adduced. 
j Experiment .—Five grains of green sulphate ef iron taken and 
dissolved in fifty measured grains of cold distilled water: to this 
added, from the end of a dropping-tube, six drops of diluted nitric 
acid, spec. grav. 1 * 280 . On applying heat to this mixture, it ac¬ 
quires a dark olive colour, arising from decomposition of the nitric 
acid by the protoxide of iron and absorption of the nitric oxide by 
the ferruginous solution. When the mixture is heated to ebullition 
this colour disappears, and is succeeded by the ordinary yellow co¬ 
lour of a solution of peroxide of iron. To the solution of the sul¬ 
phate of iron, thus altered by the action of nitric acid, an aqueous 
solution of acetate of potash, containing one tenth of its weight of 
the acetate, is to be added, in the quantity of two hundred grains 
measured. The mixture, on this addition being made, changes to 
a dark reddish brown colour, nearly as intense as that of port wine. 
The mixture is now to be diluted with its own volume of water, and 
heat applied until it boils; the ebullition continued for about two 
minutes. The peroxide of iron begins to separate as the heat ap¬ 
proaches the boiling-point, and in a short time the whole peroxide 
is detached. On filtering the mixture whilst hot, the fluid which 
passes through the filter appears colourless, and on addition of the 
the triple prussiate of potash, affords neither precipitate nor blue 
tinge indicating the presence of iron. The powder remaining on 
the filter, well washed with hot w’ater, is of a clove brown colour. 
The addition of the nitric acid with subsequent ebullition is es¬ 
sentially requisite to the success of this experiment; for if the 
green sulphate of iron be employed without the addition of nitric 
acid, on adding the solution of acetate of potash, and causing the 
mixture to boil, no change of colour to reddish brown is found to 
take place, but a black powder separates, and the mixture when 
filtered affords a fluid of a strongly ferruginous taste, yielding an 
abundant precipitate, of a bluish white colour, with the triple prus¬ 
siate of potash; thus proving that the conversion of the oxide of 
iron into peroxide must precede the addition of the acetate of pot¬ 
ash, which is otherwise incapable of separating the oxide of iron 
from the acid. 
When a solution of the green muriate of iron is treated in a man¬ 
ner similar to that above described, by converting the protoxide of 
iron into peroxide by nitric acid, and decompounding the solution by 
acetate of potash and heat, the same effects are produced as in the 
green sulphate of iron. 
If to a solution of peroxide of iron, produced by the method 
above described, a solution of the oxide of manganese is added, 
then solution of acetate of potash and heat applied, a similar depo¬ 
sition of peroxide of iron takes place ; and the filtered liquor, on 
addition of triple prussiate of potash, affords a cream-coloured de¬ 
posit unmixed with any blue tinge : the peroxide of iron has there¬ 
fore remained on the filter, and the oxide of manganese in solution 
