In one of my projects (which is about alpha-voltaic cells, don't worry, I know that thorium isn't a strong alpha source, it's only for measurements) I would need to get water soluble thorium compound from a small sample of thorium dioxide for purification with selective reactions and further measurements. Would any mineral acid work? I found some sources and publications on the internet by google searching but the biggest amount of information I could get is that
"...Several hot acids can solve it..."
Which is not nearly as accurate as I would need it because I don't want to spend the budget of the project on expensive acids which doesn't even work instead of better equipments. (Their price is from their necessary purity)