The recoveries of iodine in L-Na-thyroxinate were determined by an ash
ing method at 200 similar to 550 degrees C, using three kinds of cruci
bles. Also the effect of the aqueous extract of ''Kombu'' Laminaria ja
ponica and the artificial ''Kombu'' extracts on the recovery of iodine
were estimated. The highest value of recovery of iodine was obtained
by ashing used in a platinum crucible with alkali at 400 degrees C. Ex
cept ashing at 400 degrees C, increasing. of ashing time showed a decr
ease of recoveries. When ''Kombu'' extract was added to the sample, th
e recovery of iodine increased remarkably. It will the effect of the m
ixture of Ca-alginate, mannite and several inorganic element cortained
in the aqueous ''Kombu'' extract.