Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydrochloric acid : HCl
sodium hydroxide : NaOH
pyrogallol : C6H3 (OH)3
sodium carbonate : Na2CO3 . 10H2O
Class:
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elem=C
redox
Summary:
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Pyrogallol is quickly oxidized in alkaline environments by oxygen from the
air. The more alkaline, the faster this reaction proceeds.
The black oxidation products are affected by acid, but the pyrogallol is
not recovered by the acid.
Description:
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Add some solid sodium carbonate to a solution of pyrogallol: The liquid turns
brown, when shaken and brought in contact with air.
Add some solid NaOH: The solid dissolves and the liquid turns reddish/purplish
brown. After shaking for a little longer time (with air-contact), the liquid
turns almost black.
Add an excess amount of HCl (10% by weight): The liquid becomes much lighter
and its color becomes orange/brown.