ON HYDRATED PEROXIDE OP IRON. 
3 
from which the metal does not spontaneously pass by expo- 
sure or prolonged keeping. 
If it undergo no change from these causes, how can age 
affect it, or why must it be fresh? Will the carbonic acid of 
the atmosphere, by combining with it, neutralize its proper- 
ties, and thus affect its value? Such is not the case. Perox- 
ide of iron has less affinity for carbonic acid than the protox- 
ide, so much so, that the precipitated carbonate of iron, which 
is a protosalt, when first formed, loses nearly all its acid, by 
its base passing to the maximum of oxidation, as is well known, 
and established beyond a doubt. If kept with any kind of 
care, carbonic acid is the only acid to which the oxide could 
be exposed, and we have seen that carbonic acid opposes no 
barrier to the preservation of the oxide. Theory, then, affords 
no reason why the antidote should be freshly prepared. Ex- 
perience gives us an equally strong reason against it. In. the 
latter part of September, or beginning of October, 1837, I 
was called upon in great haste for some freshly prepared an- 
tidote for arsenious acid, for a patient suffering from the poi- 
sonous effects of arsenic; with all possible expedition the 
antidote was prepared, but too late for the relief of the victim; 
although no time had been unnecessarily lost, the patient 
expired as the first doses were administered. During this 
preparation, which was the first I had made of this oxide, it 
occurred to me forcibly, that if it were suffered to remain dif- 
fused through the water in which it had been washed, that it 
would always be in the condition of a recent precipitate, and, 
in accordance with this view, it was so put aside. The anti- 
dote remained in the laboratory of the University of Mary- 
land, unnoticed and untouched, except on one occasion, when 
it was exhibited to the medical class of the ensuing winter, as 
a specimen, until June 1st, 1838, when I was called upon by 
my friend, Dr. Thomas, for some of the antidote. Having 
none other to supply him with but this, prepared, at the least, 
eight months before, recourse was had to it. The result of 
its use is detailed by the doctor in the American Medical 
Library and Intelligencer, of July 16th, 1838. It is only ne~ 
