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Topic: Gravimetric Determination of Sulfate Troubleshooting  (Read 1726 times)

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Offline n2ro

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Gravimetric Determination of Sulfate Troubleshooting
« on: October 22, 2014, 03:48:24 PM »
Hi There,

I have a bit of a problem I'm stumped with regards to the Gravimetric Determination of Sulfate. So here's the process & problem

Start by precipitating out the sulfate with a barium chloride solution, over heat. The precipitate is then filtered out into an ashless filter paper, put into a crucible, and the paper is burnt off. The mass of the barium sulfate is then taken (minus crucible).

The lab is very similar to this one and is pretty standard first year stuff.

Over three lab sections, the amount of sulfate determined was on average 15-20% below what we know is in the sample.

I've checked all the stock solutions, Na2S04, BaCl2, HCL - and ensured they are at the right concentrations.

What could be causing such a loss of sulfate? Any suggestions would be appreciated!


Offline Borek

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Re: Gravimetric Determination of Sulfate Troubleshooting
« Reply #1 on: October 22, 2014, 06:17:34 PM »
First thing I can think of - reduction of sulfate to sulfide by the carbon from the filter paper?

I know it can be a problem, but it would be rather surprising if you will get reproducible result.
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