DETECTION OF IODINE BY CHLOROFORM. 
161 
ON THE ESTIMATION OF IODINE IN ORGANIC SUBSTANCES BY 
MEANS OF CHLOROFORM. 
By M. Rabourdain. 
The detection of iodine by means of starch paste leaves nothing 
to be desired as regards sensitiveness; but this is no longer the case 
when the quantity of iodine in organic substances has to be deter- 
mined. Chloroform may be advantageously placed by the side of 
starch as a test for traces of iodine, for by means of this reagent its 
presence may be detected in a liquid containing less than one hun- 
dred thousandth of its weight. If we take 10 grms. of a liquid con- 
taining one hundred thousandth of its weight of iodide of potassium, 
add to this liquid 2 drops of nitric acid, 15 to 20 drops of sulphuric 
acid and 1 grm. of chloroform, the latter after agitation acquires a 
very distinct violet tint. 
I have endeavored to turn to account this remarkable property 
which chloroform possesses of removing from water the iodine which 
it is capable of holding in solution in the free state, and of acquiring 
a violet color, in order to estimate approximately the iodine in 
organic substances, and especially in cod-liver oil, so largely em- 
ployed in medicine at the present day. 
I take 50 grms. of cod liver oil, which I mix by agitation in a 
phial with 5 grms. of caustic potash dissolved in 15 grms. of distill- 
ed water, and heat this mixture in a large iron spoon in order to 
destroy the whole of the organic matter; the cinder is exhausted 
with distilled water, to remove the soluble portion ; as little water 
as possible should be employed ; the liquid is filtered ; 10 drops of 
nitric acid and of concentrated sulphuric acid are added, taking care 
to cool the mixture; 4 grms. of chloroform are then poured into it, 
and the whole well shaken. After a time the chloroform is depo- 
sited, colored violet; the supernatant liquid may be decanted, and 
the chloroform solution be washed with water without depriving it 
of its color. 
On the other hand, a normal liquor is prepared containing 1 cen- 
tigrm. of iodide of potassium in 100 grms. of distilled water, so that 
10 grms. represent, 1 milligrm. of iodine. We now take 10 grms. 
of this solution, 29 drops of sulphuric acid and 4 grms. of chloroform; 
by agitation, a colouring is obtained, which is compared with the 
tint furnished by the cod liver oil ; in general it is necessary to add 
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