EXTRACTION OF IODINE FROM DILUTE SOLUTIONS. 30l 
ART. LXXX. — ON THE MOST ADVANTAGEOUS METHOD OF 
EXTRACTING IODINE FROM DILUTE SOLUTIONS, 
By J. Persoz. 
Now that iodine is so extensively used in medicine, and 
that its price is constantly on the increase, the want is felt 
more than ever of extracting it with the greatest economy 
both from the waters which contain it naturally, as from 
those of baths into the composition of which it enters, and 
even from the urine of the patients submitted to a course of 
iodine. Soubeiran, finding the process previously followed 
for the extraction of the iodine from the mother-waters of 
the Varech sodas too tedious and expensive, proposed to 
precipitate this body by sulphate of copper, to which a cer- 
tain quantity of iron filings was added, with a view to re- 
duce the periodide of copper to the state of protiodide. 
Subsequently the protosulphate of iron was substituted for 
the iron filings. 
The irregularity of the results obtained by both these pro- 
cesses must have struck every one who has tried them ; it 
is therefore not surprising that a more certain method has 
been proposed as a substitute. MM. Labiche and Chantrel 
have described one which is based upon the insolubility of 
the iodide of starch, but which in practice presents a diffi- 
culty which these gentlemen seem to have overlooked. In. 
fact, iodine combines with starch only when it is in a free 
state; it is consequently requisite to liberate it from its 
combinations by means of chlorine, and this presents an 
insurmountable difficulty. 
Having been called upon to examine this question, I found, 
in the first place, that the protacetate of iron, substituted for 
the protosulphate, produces a more rapid reduction ; but as 
it is impossible to reckon upon a regular precipitation of 
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