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Topic: Gravimetric Determination of Sulfate Troubleshooting  (Read 1614 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 http://www.csudh.edu/oliver/che230/labmanual/gravsulf.htm 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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