EXTRACTION OF IODINE FROM KELP SODA. 
225 
small quantities at a time, until no more sulphur is precipi- 
tated. This clarified liquor is put into large vessels, which 
must not be quite rilled, to allow the liquor to be stirred 
from time to time. 
The bottles having been placed upon a table, a current 
of chlorine gas is directed to the bottom of the liquor they 
contain. This gas must not be disengaged too rapidly, 
otherwise a great part of it will be lost by traversing the 
liquor without being dissolved : attention to this is also 
necessary, in order to ascertain when to stop. It is impor- 
tant that the liquor should be agitated as often as possible, 
to enable it to combine with the chlorine gas which accu- 
mulates in the empty part of the bottles. 
The chlorine gas, which is mixed with these mother- 
liquors, acts first upon the bases of the iodides, saturates 
them, and separates or precipitates the iodine ; this latter 
appears at first in the form of a reddish substance, which 
thickens the liquor, but it soon forms into brown flakes, 
which fall to the bottom. When the liquor appears no lon- 
ger to be coloured red, a small quantity must be poured into 
a glass, and left for a time to allow the iodine floating 
therein to settle ; after which a few drops of concentrated 
solution of chlorine are poured into the clarified liquor : the 
passage of the chlorine must be discontinued as soon as the 
solution ceases to thicken the mother-liqour, which, on being 
left in a quiescent state, allows the iodine to settle at the 
bottom in the form of a thick layer of brilliant brown flakes, 
If the iodine is required in large flakes, the supernatant 
liquor may be decanted off immediately, and washed in a 
small quantity of cold water ; it is then to be put into a re- 
tort of glass or porcelain, and sublimed ; a long tube of 
glass, of sufficiently large diameter, being adapted to the 
neck of the retort. The iodine is volatilized by the heat hi 
the form of violet coloured vapors, which are first conden- 
sed in the neck of the retort, and afterwards in the tube, in 
the form of small plates or flakes, having a metallic lustre 
21* 
