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SO2 Determinations Using Rankin

Hi,

When doing determinations using a rankin, you add mixed indicator to the Hydrogen peroxide in the pear shaped flask. You then titrate until an end point is reached (ie the colour changes). You then perform the rest of the procedure and re-titrate back to the same end point to work out your SO2 levels.

My question is once you have completed your determination, if wish to perform a second determination, do you need to change the indicator / hydrogen peroxide / NaOH solution in the pear flask?

I wonder because you are starting from the same point (ie having titrated until an end point is found)...

Any info would be appreciated

AB1

Reply to
ab
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I dunno for sure, but I've wondered that same thing about doing TA's. Why NOT re-use the same solution time after time? You're starting at pH 8.2 anyway.

For SO2 measurements, though, I definitely throw out the solution and start over. I can't defend that decision, but SO2 measurments are so important that I don't want to take any chances.

I'll be interested to hear what other people say.

Dave

**************************************************************************** Dave Breeden snipped-for-privacy@lightlink.com
Reply to
David C Breeden

In a commercial environment, we habitually reuse the solution up to half a dozen times.

Reply to
Andrew L Drumm

Definitely reuasable. The H2O2 is quite reactive and loses it's "trapping capacity" rather quickly ie........don't save for another day.

Reply to
BooDee

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