Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
-----------------
potassium ferricyanide : K3 [Fe(CN)6]
sulphuric acid : H2SO4
oxalic acid : HOOC COOH . 2H2O
vanadyl sulfate : VOSO4.5H2O
Class:
------
elem=V,Fe
coordination
Summary:
--------
Vanadyl ions do not precipitate with ferricyanide, when a large excess
amount of oxalic acid is present. Without the presence of oxalic acid
the two compounds form a green/yellow/brown precipitate (see other
experiments).
Description:
------------
Add a large excess amount of oxalic acid to a solution, containing acidified
vanadyl sulfate (acidified with some sulphuric acid): The oxalic acid partly
dissolves. The color of the liquid changes slightly, it changes from bright
blue to a slightly duller blue. The liquid remains clear.
Add a volume of water, a few times the original volume of the dull-blue
liquid: The remaining part of the oxalic acid dissolves.
Add a solution of potassium ferricyanide to the dilute dull blue solution:
The two liquids mix. The resulting liquid remains clear and becomes green
with a blue shade.
Add part of a black and white photo to the green liquid and agitate for a
few minutes: The black of the photo is changed to a bright yellow colour.
This formula may be the basis of a vanadium-yellow toner.