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Testing a drink for protein
A drinks company claims that a drink contains sugar, protein and fat.
Describe how a student could test the drink for protein. Give the colour of a positive result.
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Marking points
- 1 Adds Biuret reagent / solution or the accepted hydroxide-and-copper-sulfate reagents.
- 2 Gives an accepted positive colour: mauve, purple, lilac, or pink-purple.
Full-mark answer
Add Biuret solution to the drink. A positive result is mauve or purple.
Why this answer loses marks
Add Biuret solution and look for any colour change.
The reagent is suitable, but the positive observation must name an accepted colour rather than saying only that it changes.