276 
ADULTERATION OE OLIVE OIL. 
ideci to the test, we at once added the iron solution, and the moment contact 
between the two liquids occurred the blue colour showed that the formation of 
Prussian blue had, to a certain extent, been the result. After the addition of a 
solution containing 114 minims of solution of perchloride of iron, and grains 
of green vitriol, muriatic acid was added till the excess of magnesia and the 
excess of proto-peroxide of iron had been dissolved. Prussian blue was left iD 
abundance. On now at once filtering, and adding to the filtered liquid a few 
drops of a solution of persalt of iron, no Prussian blue was formed,* * showing the 
absence of any ferro-prussiate. On now adding aqua potassse to neutralize the 
excess of acid and throw down the iron in solution, no tinge of blue was pro¬ 
duced, not even on adding an excess of dilute muriatic acid. The precipitate 
entirely dissolved to a clear solution. The complete absence of prussic acid was 
thus proved. All of it had been completely removed. 
We prepared as above another quantity of magnesia emulsion mixed with 
prussic acid, and, after adding the iron solution, the liquid, having been filtered 
from the mixture, was without delay distilled, and on testing the distillate, it 
neither answered to the Prussian blue nor to the silver test; it contained no 
prussic acid. 
We believe ourselves justified in now giving, as the antidote for prussic acid, 
magnesia and a proto-persalt of iron, thus :—Make into a smooth cream, with 
water, from 1 to 2 drachms of calcined magnesia. Give the emulsion to the 
patient, then give, in water, a solution of 16 minims of perchloride of iron, and 
12| grains of green vitriol. These numbers, being in excess of the theoretical 
quantity, were those used in our experiments. Should it be supposed that so 
much as 400 minims medicinal prussic acid had been taken, of course four times 
the quantity of the iron compound necessary for 100 minims should be given, 
but without altering the quantity of magnesia. 
Although calcined magnesia, alone , slowly dissolves in prussic acid, yet in the 
presence, simultaneously, of a large excess of magnesia and the solution of a 
proto-persalt of iron, the reciprocal action resulting in the formation of a Prus¬ 
sian blue seems to be almost instantaneous. 
ADULTERATION OF OLIVE OIL. 
TO THE EDITOR OE THE PHARMACEUTICAL JOURNAL. 
Sir,—When bringing the subject of cotton-seed oil before the British Phar¬ 
maceutical Conference last month, I did not anticipate having so good an illus- 
Wlien freshly-precipitated Prussian blue is rubbed up with calcined magnesia in consider¬ 
able excess, after a short time, the mixture having been collected upon a filter and washed 
witli distilled water, it will be found that almost all the Prussian blue has been converted into 
proto-peroxide of iron, along with a simultaneous corresponding formation of fervocyanide of 
magnesium, as may be proved by the addition of a solution of a persalt of iron to the filtered 
liquid, whereby almost all the Prussian blue is reproduced. This reaction does not take place 
when an excess both of magnesia and of the iron solution is used, as in the case of the antidote; 
* or > “ q ie mix; ture of Prussian blue, proto-peroxide of iron, and magnesia thus obtained be di¬ 
gested for a long time with water, and that at the temperature of the living body, barely a 
trace of Prussian blue is produced upon the application of a solution of persalt of iron to the 
filtrate. In this case the excess of iron in the form of precipitated oxide, along with the Prus¬ 
sian blue, appears to prevent the Prussian blue from being decomposed by the magnesia, as 
would occur with this substance by itself. Two explanations of this remarkable result suggest 
themselves: either a compound, stable towards magnesia, may be formed between the Prussian 
blue and the proto-peroxide of iron, or this last substance by enveloping, and thus shielding the 
I russianblue from the action of the magnesia, may prevent the result that would otherwise be 
produced. 
