306 
Selected Articles. 
paration; for, when it is large and not full, the ioduret deli- 
quesces nearly as rapidly as when it is exposed to the free 
action of the atmosphere. When the flask is broken and the 
ioduret bottled before the mass is cold, deliquescence also 
takes place ; a peroxide of the metal is formed, and iodine is 
evolved. 
Precautions necessary for preserving both Preparations. — 
The ioduret requires to be well secured from the influence of 
the atmosphere ; both on account of its deliquescent property, 
the rapid oxidizement which the iron undergoes when deli- 
quescence occurs, and the consequent decomposition which 
takes place. It is important to prevent this state of things, 
as the peroxide of iron is inert as a medicinal agent ; whilst 
the free iodine, extricated during its formation, alters alto- 
gether the virtues of the medicine. This partial decomposition 
of the ioduret is rendered immediately apparent, on dissolving 
it in twenty times its weight of distilled water and filtering; 
instead of a permanent, clear, very pale greenish yellow, we 
obtain an ochre-colored or brown solution, which soon becomes 
turbid, and gradually deposits an ochre-coloured completely 
insoluble precipitate. Much of the ioduret usually prepared 
both by many chemists and druggists, and also general prac- 
titioners, is of this description ; and to this we may refer some 
of the disappointment and discrepancy of opinion of different 
practitioners respecting the operation of the medicine in similar 
cases. Even when the ioduret has been carefully prepared, 
and is good of its kind, it often contains a little free iodine; 
but it is chiefly owing to the carelessness of assistants and ap- 
prentices, in compounding prescriptions, by frequently ex- 
posing the ioduret to the air, that its properties, and conse- 
quently its medicinal powers, are impaired ; hence, it is pre- 
ferable to keep it in solution, or in the state of the hydriodate. 
If the solution be prepared with a definite quantity of iodine, 
as already described, it will keep without changing its cha- 
racters; but, as it is usually made by dissolving the ioduret 
in distilled water, it requires to be rendered neutral by the 
following means. Introduce into a flask, the solution of any 
