Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydrogen peroxide : H2O2
sodium thiocyanate : NaSCN
sodium hydroxide : NaOH
vanadyl sulfate : VOSO4.5H2O
Class:
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elem=V
coordination
Summary:
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Vanadyl builds an intensely colored complex with thiocyanate in acidic
environments. In alkaline environments this complex is destroyed.
When H2O2 is added, this complex is destroyed as well, but in this
case some heating is required.
Description:
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Add a large excess amount of NaSCN to an acidic solution of vanadyl sulfate:
The solid NaSCN dissolves and the liquid turns intense dark blue (original
color was sky-blue). The liquid remains clear.
Add an excess amount of a solution of NaOH: The liquid becomes turbid for a
moment, but quickly it becomes clear again and the color changes from
intense blue to brown.
Add some H2O2 (3% by weight) to the intense blue liquid and heat: The liquid
becomes pale blue/green (mix of vanadyl and pervanadyl????). A pale yellow
precipitate is formed as well, this probably is sulfur, coming from the
thiocyanate.