The saddest part of the story was his ignorance of the basics that could have had him doing a better job.
For example, the old Coleman mantles are treated with thorium nitrate, which could have been rinsed out and concentrated with water. Once fired, the ThO2 is formed. This is also true of the modern yttrium mantles. He did not have to ash them, thereby causing so much dilution. Nuclear reactions do not care about the compound, unless it contains neutron absorbing elements like cadmium.
If he wanted an alpha source, raiding Staticmaster brushes would have been much more rewarding. A milligram of polonium emits as many alpha particles per second as 5 grams of radium. The energy released by its decay is so large that a capsule containing about 0.5 grams reaches a temperature above 500K. Since a->Be>-oN1 only has a yield of 1 in 10^4 or so, the higher alpha flux from Polonium would have greatly helped him.
In short, it was a bungled and pathetic effort, that could have been vastly improved with a half an hour on the Web.
"C" for effort, "F" for Style.
The water would release the Th from the Th(NO3)4? (Assuming Th valence of 4)