Chapter 2 The nutrients in food
Read our general notes on Risk Assessment
I was wondering if you could give me some information on the reaction between ascorbic acid and NBS solution. I have recently done a practical on it and am writing it up. I am in desperate need of more sources.
Igloo says
I assume that you have titrated your solution of ascorbic acid with the standardised NBS solution, using acidified iodide ions as indicator.
I believe that the sequence of events is as follows, though I have not been able to find any web reference to confirm it.
NBS (N-bromosuccinimide) is a strong oxidising agent, and in this reaction probably dehydrogenates the ascorbic acid, forming what biochemists call “dehydro-ascorbic acid” in the process:
Once all the ascorbic acid has been destroyed, the NBS oxidises the iodide ions to iodine molecules which give the blue-black colouration with starch. This second reaction probably takes the form:
Try to find confirmatory (or otherwise!) information before committing any of this to your write-up. Remember to credit www.chemistry-react if you use the information supplied here.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
back to Chapter 2 The nutrients in food
Rate this page or react
Share your views on this page, 18 ratings so far
, rated at 
updated: 12 January 2008
