226 
ANTIDOTE TO PRUSSIC ACID. 
take their place. The affinity of prussic acid for iron, is 
not of itself sufficient to effect this result, but the two affi- 
nities — that of prussic acid for iron, and sulphuric and mu- 
riatic acids for the alkali — acting in concert, do so at once. 
Nine equivalents being 70 x 9=630, four grains of peroxide 
of iron will require 15.7 grains carbonate of potash, thus 
160 : 630 : : 4 : #=15,7. 
According to the above calculation, one drachm of tincture 
of muriate of iron and 9.75 grains of green vitriol in solu- 
tion, on being added to a liquid, containing 15.7 grains of 
carbonate of potash, can separate prussic acid from that 
liquid if present, whether in an open vessel or in the living 
stomach, to the extent of 5.6 grains ; but in fact, it will be 
found that an amount equal to that is not separated. This 
is readily understood, when it is recollected that the com- 
mon carbonate of potash is a very deliquescent salt, and 
further, that it is by no means pure ; and besides this, the 
tincture of muriate of iron contains an excess of acid, which, 
with the alkaline carbonate will form chloride of potassium, 
which has no affinity for the prussic acid, but must have the 
effect to the extent of the quantity formed, of diminishing 
the amount of carbonate really effective in precipitating 
prussic acid. The practical result of these various disturb- 
ing causes, is, that on precipitating the prussic acid by the 
method above explained, from a liquid containing the acid 
in considerable excess, the Prussian blue, separated by fil- 
tration and converted into peroxide of iron, weighed, after 
ignition, instead of seven grains, only one-third of that num- 
ber. So that instead of 5.6 grains of anhydrous prussic acid 
being removed, the real quantity was only a third of this; 
but it must be kept in mind, that if a quantity of acid ex- 
ceeding that should be taken, it is but too probable that the 
unhappy individual would perish too quickly to allow of 
any means whatever being used. To make up to a certain 
