MadSci Network: Chemistry

Subject: What is the chemistry of quantitative Benedict's solution

Date: Thu Jan 27 06:14:26 2000
Posted by Tony Tooth
Grade level: 10-12 School: King's School
City: Ely State/Province: Cambs Country: UK
Area of science: Chemistry
ID: 948975266.Ch

In a Food Scienec Topic in the Nuffield A Level Chemistry course in the UK 
quantitative Benedict's is used to determine the glucose content of drinks 
after standardisation against a glucose solution of known concentration. I 
can complete the calculation and know that quantitative Benedict's is used 
to introduce thiocyanate ions so that white CuSCN is precipitated instead 
of brick-red Cu2O (presumably to make the end-point easier to see. However 
methylene blue is suggested as an indicator and I can't discover its 
function or how it 'indicates' and I have never been able to find or work 
out an equation for the reaction of glucose with Benedict's solution or 
even the actual formula of the comnplex Cu (II) ion in Benedict's 
solution. I, and my student's, would be very grateful for this 
information.  Many thanks

Re: What is the chemistry of quantitative Benedict's solution

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