HYDRATED PEROXIDE OF IRON. 
31 
be inverted without its changing its position. This, when 
diluted, removed the arsenic in three hours. 
G. A specimen twelve months old, and after twenty-four 
hours contact with it, the solution yet contained arsenious 
acid. 
H. A specimen, precipitated three months ago, was found 
to remove the arsenic in ten or fifteen minutes. 
/and J. Specimens precipitated for the occasion, removed 
the arsenic in five to eight minutes. 
In looking over the above results, and comparing them, the 
difference in the activity of the specimens is quite apparent, 
and those which are the least active are on the side of age. But 
independent of any influence that mere age may have in its 
deterioration, other circumstances most probably influence 
the powers of the preparation. It was invariably found, that 
those[specimens which were most diluted, that is to say, which 
had the largest proportion of water admixed, all other cir- 
cumstances being equal, were least active ; whereas, those 
which preserved the state of magma, having little water mix- 
ed with them, were most active. Thus specimen F, made at 
the same time as D, was much more active. By having 
much fluid associated with them, the particles of the hydrated 
oxide, after being kept some time, appear to contract in some 
way, so as to take up less space in the bottle. It is not pro- 
bable that this preparation undergoes any change through the 
agency of the atmospheric oxygen, the iron being already at 
its maximum of oxidation; hence, the most accurate ex- 
clusion of the air, will not prevent its deterioration, and this 
must be attributed to another cause. Orfila has stated, in a 
note to the Academy,* that colcothar, which is an anhydrous 
peroxide of iron, possesses no antidotal power, that is to say, 
it does not combine with arsenious acid. He says that if two 
millegrammes (.3 of a troy grain) of arsenious acid be boiled 
* American Journal of Pharmacy, Vol. xiii. page 331, from Journal 
de Chim. Med. 
