ANTIDOTE TO PRUSSIC ACID. 
225 
tains about thirty grains of peroxide of iron, one drachm 
must contain very little less than four grains ; and as the 
Prussian blue resulting from the action of the antidote is 
composed of two equivalents of sesquicyanuret of iron, and 
three equivalents of protocyanuret, 
3 Fe Cy-f 2 Fe 2 Cy 3 , 
two equivalents of the sesqui or peroxide 80 x 2=160 with 
the proper quantity of a protosaltof iron, will separate nine 
equivalents, or 226.51 of prussic acid: 
thus H Cy 1 equivalent=27.39 x 9=246.51. 
Taking as the basis of our calculation the quantity of perox- 
ide of iron contained in tincture of muriate of iron, it will 
be found by the rule of proportion, that one drachm of the 
tincture, containing four grains will neutralize 5.6 grains of 
real or anhydrous prussic acid, or 280 grains of the strength 
prescribed by the London College, thus 
160 : 246.51 : : 4 : x=5.6. 
The relative quantity of sulphate of the protoxide of iron, 
or green vitriol, can also be learned by proportion, for as 
two equivalents of peroxide of iron are united to three equi- 
valents of protocyanuret of iron, to constitute Prussian blue, 
every two equivalents of a peroxide of iron in solution must 
be mixed with three equivalents of a protoxide of iron also 
in solution ; and as the equivalent of protosulphate of iron 
is 130, three equivalents will be 390, calculating from these 
figures, it will be found that four grains of peroxide of iron 
will require 9.75 grains of green vitriol, for 
160 : 390 :: 4 : #=9.75. 
In the same way the correct quantity of salt of tartar, or 
carbonate of potash, may be found. The equivalent of this 
is, in round numbers, 70, of which nine equivalents must 
be present, along with the prussic acid to seize the nine 
equivalents of the strong acids, sulphuric and muriatic, con- 
tained in the mixed iron salts, to allow the prussic acid to 
