144 
ON AN ANTIDOTE AT ONCE FOR 
hours’ contact allowed before filtration, it will be found that the liquid is free 
from arsenic. On now adding the solution of other 5 grs. of* arsenious 
acid, giving the same care in stirring, and an equal time to the mixture for 
digestion, it will be found that the filtered liquid gives distinct traces of 
arsenic, but not more than, on comparison, is given by ^ of a grain of 
arsenious acid in solution. 
The practical inference that seems to be fairly deducible from the experi¬ 
ment here detailed is that, although the hydrated oxide of iron cannot quickly 
remove more arsenic than one-eighth of the weight of oxide of iron con¬ 
tained in it, yet it continues gradually acting to such an extent that, in the 
end, it can actually absorb nearly double that quantity. 
There is a method of preparing the hydrated oxide of iron as antidote for 
arsenic, with caustic magnesia in place of either a fixed or volatile alkali; 
and, as thus prepared, its assimilating power on arsenious acid being com- 
p ete, and its preparation easy and speedy, it will perhaps be considered by 
most toxicologists to be the best form of the antidote. 
Measure off 3(37 minims of liquor ferri perchloridi into a glass, dilute 
with 3 or 4 oz. of water, then rub up, in a mortar, 90 grs. of calcined mag¬ 
nesia, imo a, cream, with about two ounces of water; this is at once added to 
the iron solution, and immediately briskly agitated with a glass rod. In 
about a minute the mixture, previously fluid, sets into a gelatinous mass of 
hydrate of peroxide of iron, with the production of a slight degree of heat, 
0n * ur , er stirring again becomes thin, and now consists of a mixture 
o grs. of peroxide of iron, and 142'5 grs. of chloride of magnesium, 
W1 ,., fh sma ll f* ce . s f ma gResia. If the case does not contra-indicate the 
exhibition of chloride of magnesium, the antidote is ready for immediate use ; 
but, it otherwise, it is very easily removed. To get quit of it add 3 or 4 
ounces oy water, mix and throw the whole upon a muslin or calico cloth laid 
into a basin, bring together the ends of the cloth, grasping them firmly in the 
iett hand, and with the right press out the liquid steadily and moderately 
quick. Alter the liquid comes in drops, remove the mass from the cloth into 
a clean mortar, and then rub it into a smooth cream with a little water. The 
antidote is now ready for use, and is only contaminated with a quantity of 
chloride of magnesium, altogether insignificant. The whole operation can be 
easily finished m about five minutes. 
If it should be considered necessary to get rid entirely of the chloride of 
magnesium, filtration can be adopted, and the mixed oxide of iron and mag- 
nesia washed till the washings come away tasteless. In consequence of the 
ycirate being mixed with magnesia, the filtration is very rapid. 
t would be a great mistake to think that magnesia itself could act as an 
antidote to arsenious acid ; any one can prove this for himself by the follow¬ 
ing experiment: Dissolve a Quantitv of sulnliate of mncmpsin anffipip-nf. +r> 
J D. ui coaemous acia irom solution. 
Yve here introduce a literal tran sin firm n f Unnom's __ :j. 
“It is w since I have been ted to the observation that a sZEoT^en’iousadd 
“ Gottingen , May 1 , 1834 . 
