34 HYDRATED PEROXIDE OF IRON. 
not do away with the evidence of those experiments, viz. that 
hydrated peroxide of iron deteriorates by age, etc.* 
Orfila again observes, " MM. Nonat, Deville and Sandras, 
have advised, and with reason, to use in preference the dry 
hydrated peroxide, because it contains in the same weight 
four times the amount that it does in the state of magma; and 
they also advise to give 16 grammes of the hydrated perox- 
ide for each grain of arsenious acid to be neutralized." 
It cannot be doubted that the dry hydrated oxide can be 
administered in less space; but at the same time it is equally 
true that the recently precipitated oxide is much more active, 
and should always be employed in preference, and besides 
the recent article from its levity would remain perfectly sus- 
pended in the fluids of the stomach and be active at every 
point. 
The case spoken of by Dr. Fisher in his elaborate paper on 
this subject (in the 12th vol. of the American Journal of Phar- 
macy) where an oxide eight months old was successfully em- 
ployed, agrees with the conclusions arrived at in the above 
experiments, as it has been seen that an oxide two years old, 
in one instance, removed the arsenic in three hours. But at 
the same time that we agree with Dr. F, that every apothe- 
cary should keep the oxide ready prepared, we believe that in 
all cases, when the recent is attainable, it should be resorted 
to in preference as being more active. 
Method of preparing the hydrated peroxide. — Dr. Fisher 
recommends that this preparation be made directly from 
the metal, by first forming a sulphate of the protoxide and 
then per-oxidizing by nitric acid, precipitating by ammonia 
and washing. This course will always give a pure prepara- 
+ Since the above was written, six grains of arsenious acid in solution 
was introduced into a half pint bottle of the antidote, containing about six 
drachms of the hydrated peroxide which had been prepared two years. 
Three weeks afterwards the filtered solution was strongly charged with the 
arsenic, notwithstanding the mixture had been frequently agitated. 
