[travis]

I'm trying to oxidize calcium sulfide or sulfate (don't have an actual chemical analysis). Ideally I'd like to  reach the calcium sulfate hemihydrate stage. However I'm not even sure I'm getting to the sulfate stage.I've tried oxidizing with hydrogen peroxide and sodium hyperchlorite and I'm not getting much strength out of either one. I've also tried calcining at various temperatures (up to 800C) and grinding back down with a miniature ball mill. Not having much luck. Is there a simple test I can do to determine whether I've even got sulfate or not. I know the specific gravity of sulfate is considerably less than sulfite, however no matter how many times I try to oxidize it it remains the same. One other question, when I'm oxidizing with the peroxide I get a reaction every time, I oxidized 20 times and still it heated back up every time. My thinking is that I should be completely oxidized if it no longer reacted with the peroxide, am I wrong?
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[kevins]

Are you use the very fine powder (prefer the 45um size) of calcium sulfide react with peroxide? Please try again.