30 
HYDRATED PEROXIDE OF IRON. 
be by the following observations, then it becomes a matter of 
some moment, both to the physician and the apothecary, to 
be acquainted with the fact and to adopt a remedy. 
Nine specimens of the hydrated peroxide of iron, all of 
which had been kept in the moist way under water, and most 
of them in bottles hermetically sealed, were treated in the 
following manner, viz. : The percentage of dry oxide which 
they severally contained having been ascertained, so much of 
each as was equal to thirty-six grains of the oxide, was placed 
in a vial, and three grains of arsenious acid, in solution, added, 
the mixture occasionally shaken, and tested to ascertain if the 
arsenic had been removed from the solution. 
A. A specimen made about four years ago, and appeared 
to be in a finely divided state. The mixture of this speci- 
men and arsenious acid was tested occasionally with ammoni- 
acal sulphate of copper, and ammoniacal nitrate of silver, for 
three days, at the expiration of which time, a portion of the 
filtered liquid was treated by Marsh's apparatus, which 
gave evidence of the presence of arsenic, although, previous 
to the addition of the solution, no spot could be obtained. 
B. A specimen two years old, in appearance similar to 
the preceding. This was treated as above, and at the end of 
three days the solution contained arsenic. 
C. A specimen two years old, apparently more dense than 
the preceding, was found equally, if not more inactive. 
D. A specimen which had a thicker consistence than any 
of the preceding, preserved its gelatinous character to a greater 
extent, and was about two years old. All the arsenic had been 
removed from the solution in twenty-four hours. 
E. A specimen nine months old, very thick in its consist- 
ence, having much less water mixed with it. This was dilut- 
ed to the proportion of the other specimens, the arsenic added, 
and the latter was entirely removed from solution in four or 
five hours. 
F. A specimen made at the same time as D, but having 
less water mixed with it, being so thick that the vessel could 
