Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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potassium tetrathionate : K2S4O6
sodium thiosulfate : Na2S2O3 . 5H2O
sulphuric acid : H2SO4
Class:
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elem=S
redox
Summary:
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The tetrathionate ion is much more stable than the thiosulfate ion in acidic
solution.
Description:
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Prepare a solution of potassium tetrathionate (K2S4O6) in water. Take a small
spatula full of solid and add this to 3 ml of water: A colorless and clear
solution is obtained.
To this solution add 1 ml of 2M sulphuric acid and wait: The solution remains
clear. Even after one day the liquid still is clear.
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Repeat the experiment with sodium thiosulfate instead of potassium
tetrathionate: After adding the acid, the liquid becomes turbid and light
yellow after just a few tens of seconds. There also is a bad sulphurous smell,
not only SO2 is smelled, but also other compounds. The smell actually is quite
bad.