What will happen if you put iodine on confectioners sugar?

If you put iodine on confectioners' sugar, the iodine will not react significantly with the sugar itself, as sugar does not contain starch, which is what iodine typically tests for. Instead, the iodine may simply stain the sugar, resulting in a darkened appearance. This is because iodine can create a colored complex with certain compounds, but in the case of pure sugar, there won't be a notable chemical reaction.