Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: yona on March 25, 2017, 12:01:53 AM
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Hello.
For a chemistry project, I made simple beer out of malted grains that I heated then cooled.
I want to measure the sugar content of my beer with Fehling titration.
Different types of sugars can be found in beer, such as glucose and maltose, which contain an aldehyde (RCHO) group, therefore the Fehling test can be used.
The sugar will reduce the ions Cu2+ into Cu+ under basic conditions with this equation:
RCOH (aq) + 2 Cu2+ (aq) + 5 OH-(aq) :rarrow: RCOO- (aq) + Cu2O(s) + 3 H2O (l)
I calculated the %m/m of glucose in rye, based on USDA's data, so there's around 0,98% of glucose in rye.
I used 75 g of rye, which sums up to around 0,735 g of glucose.
I then calculated the molarity of glucose, where the volume was 0,46 L, which gave me 0,008869 M of glucose.
After that, I am not too sure how to proceed with the titration. I searched for determination of glucose/reducing sugars by Fehling titration and found some procedures, such as:
http://corn.org/wp-content/uploads/2009/12/DEXTR.02.pdf
https://www.york.ac.uk/org/seg/salters/ChemistryArchive/ResourceSheets/sugars.PDF
http://blamp.sites.truman.edu/files/2016/01/Fehling-final.pdf
So I plan on using Dextrose (D-Glucose) Anhydrous as well.
And I am rather lost, is there a way to determine what quantities of the sample, the Fehling solutions, the amount of distilled water, the mass of dextrose, etc. that I will need to use?
Do I just pick a certain volume of the rye sample solution on my own and then try to find quantities of the other substances from it? If so, how can I proceed to do that?
I apologize for the long post.
Any help is appreciated. Thank you very much!
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http://www.titrations.info/titrant-and-sample-volume