#68716
iodine forms a stable complex with starches. starches include cellulose, which is in wood and paper towels
when
Iodine is added to either of these, it will retain that very dark color indefinitely
you can convince yourself of this by adding a little corn starch to water, and then adding one drop of
Lugols and stirring. the starch-iodine complex forms immediately.
not so with the skin, as there is no cellulose or free starch therein that is capable of forming this complex.
thus, the iodind on the wood and paper is incapable of evaporating, whereas some of that which is placed on the skin is free to evaporate.