morpheus - Most iodine tincture sold in Oz does NOT contain povidone. Those that do contain it, list it on the label.
Some 'iodine tincture' sold in Oz is just an Ethanol solution of iodine. This is different to other iodine tincture formulations. This could lead to difficulties in following extraction processes on a tincture that has a different composition. (I think the other common mixture is iodine, KI, Ethanol and water.)
I knew somebody that extracted the iodine from the ethanolic tincture simply by setting it on fire in a pyrex dish, and cooling it rapidly when all the liquids are gone. They did use the iodine produced in this manner with success but I really don't know how pure it will be. Far better to spend a little more time and extract it by normal, safer means.
Obviously if somebody _really_ wanted to try that ignition idea they'd want to ensure they took adequate precautions against the iodine vapours that almost certainly will form! They can't chase you quite like elemental Bromine will, but real nasty nonetheless.
...Anansi