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Identity HelpAcid Resistance: Benstonite vs Calcite

4th Aug 2016 00:30 UTCSteve Hardinger 🌟 Expert

Does anyone know if there is a noticeable difference in the rate of bubbling with dilute HCl between calcite and benstonite?

4th Aug 2016 01:14 UTCReiner Mielke Expert

Not sure how that is going to help you, better to test for Ba using sulphuric acid.

4th Aug 2016 02:25 UTCDoug Daniels

Using the rate of bubbling would be kind of iffy, although I would think that the benstonite would be less reactive than calcite (kinda like dolomite, or witherite). I agree with Reiner about testing for barium tho; more definitive, and simpler.

4th Aug 2016 03:18 UTCJason Bennett

Hi Reiner and Doug,

Could one of you please explain how sulfuric acid tests for Ba? This must have been something that I either a) forgot or b) was never taught... though I suspect the truth is closer to a)....

Looking at the possible reaction outcomes, I assume it would grow BaSO4 crystals... as opposed to CaSO4 which would be more soluble? Am I on the right track?

Cheers

Jason

4th Aug 2016 03:37 UTCDoug Daniels

Yes - barium sulfate is very insoluble. Ideally, you would first dissolve a piece of the sample. If there is barium in the solution, adding any sulfate (it doesn't have to be sulfuric acid) would produce a precipitate of barium sulfate. Calcium sulfate may also precipitate out (if there is calcium present); however, this will dissolve in hydrochloric acid, whereas barium sulfate won't.

4th Aug 2016 03:49 UTCsteven garza

Of course, simply doing a flame test, for barium, is a strange idea, seeing as the green would out shine the yellow; it would flash green, then change over to yellow. Does that sound like a better idea? Do NOT breathe in the fumes, as you do this - have a fan going behind you, as you do this.

Your friend, Steve

4th Aug 2016 04:09 UTCSteve Hardinger 🌟 Expert

Nine of these posts have answered my question. I'm not testing for barium. I simply want to know if benstonite is noticeably more (or less) resistant to HCl than is calcite.

4th Aug 2016 05:00 UTCDoug Daniels

Checking my references, there may not be much difference in reaction between the two, but I'm basing this on the reaction of HCl with calcite and witherite. Both are readily attacked by HCl. However, benstonite has a bit of magnesium, so that might slow the reaction slightly, but you likely wouldn't be able to tell. So, I'd say there wouldn't be a noticeable difference between the two.

4th Aug 2016 06:14 UTCsteven garza

That's why I suggested what I did; you don't test for barium & how much, you won't get an answer to your question. The flame test does that, quickly.

Your friend, Steve

4th Aug 2016 11:32 UTCAlfred L. Ostrander

Steve,

I found one rather obscure reference to benstonite indicating it was less reactive to weak HCl than calcite. Consider benstonite is in the dolomite group and the groups general resistance to HCl compared to calcite. And keep in mind the molarity of the HCl. Drop samples into very strong acid and watch them all react strongly.

Best Regards,

Al O

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