56 ON THE PREPARATION OF IODIDE OF IRON. 
ART. VII. — ON THE PREPARATION OF IODIDE OF IRON. 
By Dr. A. T. Thomson. 
Having had the satisfaction of introducing the Iodide of 
Iron, as a therapeutical agent, to British Practitioners, I feel 
anxious that its preparation, should be such as will prevent 
the rapid decomposition of the salt, and the formation of the 
Sesquioxide of Iron, whenever it is exposed to the air, whe- 
ther in the sold state or in solution, a circumatance which has 
been regarded as an objection to its employment. 
Daily experience has demonstrated that the solid salt can- 
not be preserved long, even in well stopped bottles ; and 
when the evaporation has been conducted by the aid of lime, 
and carried to the greatest point of dryness, as proposed by 
Messrs. T. and H. Smith, Chemists in Edinburgh, whose pro- 
cess has been adopted in the Edinburgh Pharmacopoeia, the 
salt is still susceptible of rapid decomposition. It is a mis- 
take, however, to suppose, as Messrs. Smith have done, that 
the result of this decomposition is a peroxide and a Periodide 
of Iron. On the contrary, it is a mixture of Iodide of Iron, 
Sesquioxide of Iron, and free Iodine. This is rendered obvi- 
ous by throwing the decomposed mass into water — the ses- 
quioxide falls to the bottom, whilst the solution, which con- 
tains the iodide, has the deep brown color of the aqueous so- 
lution of Iodine, and a powerful odor of that substance ; it in- 
stantly, also, forms the Iodide of Amidine when it is added 
to a cold solution of stnrch. Unfortunately, it has, too often, 
been dispensed in this state ; and, consequently, it has been 
productive of much injury in cases in which the Iodide of 
Iron was clearly indicated, but in which the free iodine, in 
the decomposed preparation, was likely to prove hurtful. 
With these facts in view, it is remarkable that the only 
preparation of the Iodide of Iron, ordered by the London 
College of Physicians, is the solid salt ; and that this form of 
the preparation is also ordered in the new Edinburgh Phar- 
