MadSci Network: Biochemistry
Query:

Re: Does the amount of Bendedict's solution used affect the time needed?

Date: Wed Nov 1 15:57:11 2000
Posted By: Jim Caryl, Grad student, PhD Plasmid Molecular Biology, University of Leeds
Area of science: Biochemistry
ID: 972566443.Bc
Message:

Hi Dan,

Sorry if this information comes too late for you! Anyway, I would have to say that time is an awkward but perhaps worthwhile variable to test in this experiment. A precipiate is not expected until the solution is boiling, and herein lies some of the "sub-variables" for what you propose :

- You will have to bear in mind the quality of bunsen flame, i.e. setting, gas pressure and ventilation;
- The height of the sample above the flame;
- The type of vessel in which you are heating the sample;
- and to some extents the ambient temperature (though I hardly think this is important - though perhaps it may be in south-west Wales!). All these will effect the length of time it takes to boil your sample and keep it boiling.

You are correct in stating that an equal volume of Benedicts must be used when conducting trials into this variable - as only one variable must be changed at a time.

As for whether the amount of time needed for a colour change to take place (while under heat) is affected by the amount of Benedict's solution used? I would guess so, yes. Remember that it is the Benedicts that is being reduced by the "reducing-sugar" and therefore you can imagine that there would be a time difference it the sugar's ability to proceed with this reduction if there was an increasing amount of Benedicts present.

Another thing to give thought to it that there must be a reasonable ratio of your sample (potentially containing a reducing-sugar) to benedicts solution, i.e. 1ml of your sample to 50ml of benedicts isn't really going to do much for you either way!

I apologise if my high-school chemistry is a little rusty (pardon the pun!)

Jamie Caryl
MAD Scientist


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