Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: grec08 on June 08, 2006, 03:48:37 PM
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This information is nowhere online, so any help would be greatly appreciated:
I am trying to recreate the second reaction seen here, which is the dehydration of sucrose by sulfuric acid with permanganate:
http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/FORMC/PAGE1.HTM
I would like to perform this demonstration on a smaller scale to reduce the amount of fumes released. What concentrations, or how do I go about finding the concentrations, should be used of the sugar-water solution, the sulfuric acid, and the permanganate (I will be using potassium permanganate)? And, what respective volumes of these reactants should I use in order to perform the demonstration successfully, but produce fewer fumes? How do you know this!? Thanks!
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I did something similar, but much more informally and without the permanganate. As far as the sugar-water concentration, I saturated around 125ml of water with sugar. I then added a few drops of 98% "concentrated" sulfuric acid. This worked just fine for me, but it will still produce steam, SO2, and I'm pretty sure with the heat that some of the sulfuric acid evaporated off also.
I would recommend either a fume hood or a well ventilated area. Test in small amounts first in a fume hood (or outside) so you know exactly what to expect. It really doesn't take much sulfuric acid to get this reaction going, especially if the sugar is dissolved. I also did this with just some dry sugar.
[Edit] I decided to put concentrated in quotes because it's somewhat of a relative term.
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Thank you!
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That looks like a pretty low concentration of permanganate, which is very strongly colored. If you use too much, you won't have enough SO2 to reduce it all. As far as the sulfuric acid, you want c. 98% 'concentrated' stuff.