Description of experiment
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Needed compounds:
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hydrogen peroxide : H2O2
sodium hydroxide : NaOH
glucose : CH2OH (CHOH)4 CHO
hydrochloric acid : HCl
ferric chloride : FeCl3 . 6H2O
Class:
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elem=Fe
coordination
redox
Summary:
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Ferric ions apparently form a coordination complex with glucose in alkaline
environments. Normally ferric ions give a brown precipitate in strong
alkaline liquids, with glucose the liquid remains clear.
Description:
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Add a slightly acidified solution of ferric chloride to a solution of
glucose: No visible reaction, the liquid becomes pale yellow.
Heat to appr. 60 C: Color of liquid becomes slightly more intense.
Add some solid NaOH: Around the pieces of solid NaOH a brown precipitate
is formed. On shaking everything (precipitate and NaOH) dissolves. The
liquid becomes red/brown and clear.
Add some H2O2 (3% by weight): No visible change of color. Slow formation
of a gas (probably oxygen). When the liquid is shaken, the evolution of
gas is stronger.
Add an excess amount of HCl (10% by weight): The liquid becomes yellow and
its color is much less intense, than one would expect, based on the
dilution.