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Starch / KOH buffer solution

Guest hotkarl
Guest hotkarl
in Organic Chemistry

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I've started making a buffer solution by mixing 6g iodometric starch in half a litre of water. I then added 20g KOH and heated it up a bit to get it to dissolve. I am now going to add a small amount of acetic acid, then adjust the pH to 4 using HCl. The thing is, my solution was colourless until the last of the KOH dissolved, I left it for 2 minutes (never do this!) and came back to find it was pale green! Please can someone suggest why?

What did you make it in?

 

~Scott

I made it in a volumetric flask on a hotplate.

 

Karl

You heated KOH in water?

 

Are you certain the glassware was clean?

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