[cinFLA]

"David's method purified thorium to at least 9,000 times the level found in nature and 170 times the level that requires NRC licensing."

He didn't 'purify' the thorium. It is purified by the extraction process prior to the lantern mantel manufacturing.

[Cooter]

The quote was from the original Harper's article. He didn't purify the thorium, he isolated it. Mantles are made with thorium nitrate among other compounds. Upon cure (first burn), it is converted to thorium oxide.