rocketsurgeon
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purifacation of stopbath?
I recently aquired some indicator stopbath.
so I was reading the msds and it says that its 80-90%by weight
but its 99.97% concentration. I found that it also contains bromothymol violet.
Now to the point could i separate them without distillation or using test tube distillation?
[Edited on 24-6-2013 by rocketsurgeon]
[Edited on 24-6-2013 by rocketsurgeon]
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ElizabethGreene
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Hello. Stopbath can be made a number of different ways. Can you post a link to the MSDS or the composition of the product?
What compound are you trying to isolate from it, the Acetic acid?
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rocketsurgeon
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msds
It dosn't say about concentration
And yes i would like to obtain acetic acid from the mixture.
msds
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ElizabethGreene
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This might help you get some better answers.
"I have a bottle of KODAK Indicator Stop Bath Concentrate. This is 85+% acetic acid, plus bromothymol violet as a color-changing indicator. Are
there any easy ways to extract the acetic acid from this? I don't have access to standard distillation equipment."
With that out of the way, have you tried freezing it very slowly? Acetic acid has a high melting point of 16C/61F (Wikipedia, Acetic Acid). With any
luck it should exclude the contaminants as it crystallizes.
Proposed procedure: Get a flask or jar of ice with just enough water to cover it. Place a sample of the stop bath in a test tube. Lower just the end
of the test tube into the ice bath. What you want to happen is that it freezes starting at the end of the test tube. After ?half? of the tube is
frozen, dump the remaining liquid and retain the solid. When it melts, test for the presence of the bromothymol by taking a sample of the and adding
a dilute base to see if it changes colors. If the ice bath isn't cold enough to freeze it, you can add salt to the bath to make it colder.
This is a completely untested procedure, but sounds like fun. If you haven't read the safety section of the Wikipedia page, do so now. "can cause
skin burns, permanent eye damage, and irritation to the mucous membranes. [...] burns or blisters may not appear until hours after exposure. Latex
gloves are ineffective [...]"
Is the current solution Yellow, turning blue after you add a base?
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