Description of experiment
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Needed compounds:
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potassium hydroxide : KOH
oxalic acid : HOOC COOH . 2H2O
vanadyl sulfate : VOSO4.5H2O
Class:
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elem=V
coordination
Summary:
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Oxalic acid does not seem to form a coordination complex with vanadyl ions,
or if a complex is formed, then it has a color, which is almost the same of
the color of aquated vanadyl.
Description:
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Add a large amount of oxalic acid to a solution of vanadyl sylfate (prepared
from vanadium pentoxide, dissolved in ammonia and adding sodium sulfite and
sulfuric acid and afterwards expelling excess sulphur dioxide): The oxalic
acid dissolves, the liquid remains blue. It looks as if the bright blue
vanadyl-solution becomes a little more dull-blue.
Add some solid potassium hydroxide: The solid dissolves and the liquid becomes
warm. The liquid becomes dark brown (familiar color of vanadium (IV) in
strongly alkaline solution).