ON THE PREPARATION OF IODIDE OF IRON. 57 
macopceia. But a solution of the Iodide, which is intended 
to contain about four grains and three-fourths of a grain of the 
Iodide in each fluid drachm of the solution, is, also, ordered 
by the Edinburgh College. A piece of iron wire is proper- 
ly directed to be kept in the bottles containing the solution, a 
mode of preserving the solution of a definite strength, which 
was suggested by my friend, Mr. Squire.* Although, in a 
solution thus treated the Sesquioxide of Iron is formed and 
precipitated, yet as soon as the oxidizement takes place, the 
free Iodine instantly combines with an equivalent of the 
Iron, which supplies the place of that which is oxidized, and 
the solution remains of the same strength, in reference to the 
Iodide, as when it was made, even when the bottle containing 
it is a fourth or more full of the Sesquioxide of Iron. This 
fact is readily demonstrated by filtering the solution and 
evaporating a given quantity of it, to ascertain its solid con- 
tents. The addition of the coil of soft Iron to the solution, 
therefore, obviates, in a great degree, the objection to the em- 
* The following is an extract from an article of Mr. Squire, on the sub- 
ject, published in the " Annals of Philosophy," in May, 1836 (page 79.) 
"The Protiodide of Iron was first employed in medicine in this coun- 
try by Dr. A. T. Thomson, and has since kept its character as a valuable 
tonic. The great inconvenience arising from its tendency to decompose 
when dissolved in water, is completely obviated by a coil of iron wire 
traversing the whole column of the solution, which was suggested by me, 
when it came into extensive use as a therapeutic agent, and nearly three 
years experience proves it to answer most satisfactorily the object in- 
tended ; it will preserve it perfectly neutral, even if the solution be fully 
exposed to air and light. It is true, in that case more peroxide is formed; 
but filter the solution when you will, it is perfectly colorless and transpa- 
rent as distilled water. This is a very important point, and one which 
the medical profession should be made fully acquainted with, being a 
safe test for its neutrality and purity. Any color, however slight the 
tinge, shows the presence of some iodine in a free state, or some impuri- 
ties derived probably from one of the materials employed to make it ; this, 
no doubt, has given rise to the difference of opinion as to its action on the 
animal economy. The colorless neutral compound, when diluted, has an 
agreeable flavor, similar to that of a chalybeate spring, whereas any free 
iodine gives a mawkish taste, and is liable to nauseate the stomach." 
VOL. VIII. — NO. I. 8 
