After searching old newsgroup posts, I found that aluminum sulfate is used to burn broken HSS taps and drills out of aluminum which is my present need (drill bit). Low and behold, McMaster stocks it and it arrived today. No MSDS was included. I've always laughed when MSC will include an MSDS on cutting tools like taps and end mills, and here McMaster doesn't even include them on an honest to gosh chemical :) A 3 minute web search turned up the MSDS, so no problem there.
This stuff comes in powder form. Anyone know what kind of concentration I need to dissolve the HSS? I can't reach the drill bit by mechanical methods and I thought I'd learn something new (chemical dissolving) before resorting to an EDM shop.