Re: Mystery Precipitate

Sulphide soln
Alkali sulphide on aging and atmospheric oxidation are partially
converted to polysulphides. Acidification produces a precipitate of
elemental sulphur.
Alternatively if you acidulate in the presence of an oxidant again you
get elemental S ppted.

Barium salts in strong acid soln pretty good indication of sulhate
ion.

This is all available in books. You know those things you tend to find
in libraries. Asking simple questions on the net such as the ones you
just asked tends to indicate an adversion to work.

Bob M.

On Aug 30, 1:56 am, Michael Ellis <n...@xxxxxxxx> wrote:
I'm preparing chemicals for a qualitative analysis lab. We're mixing
some 0.1 and 0.2 M solutions and getting precipitates. Here's my problem:

One of the solutions is Na2S. Whenever it is mixed with one of the acid
solutions (HCl, HNO3, or H2SO4), I get a cloudy white result. No
precipitate should form from these reactions. It's probably not metal
impurities in the acids, because those would form dark-colored sulfide
precipitates, not cloudy white. I see the same white cloudiness when
mixing the acids with Ba(OH)2, where again no precipitate should form.

If anyone knows the source of the cloudiness, I would appreciate a clue.

Thanks.


.

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