Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
-----------------
potassium ferrocyanide : K4 [Fe(CN)6] . 3H2O
potassium ferricyanide : K3 [Fe(CN)6]
sulphuric acid : H2SO4
potassium metabisulfite : K2S2O5
potassium permanganate : KMnO4
Class:
------
elem=Mn,Fe
precipitation
Summary:
--------
Manganese (II) gives an off-white precipitate with ferrocyanide and it gives
a dark brown precipitate with ferricyanide. The brown compound probably is
a manganese (IV) compound, formed through oxidation by ferricyanide.
Description:
------------
Dissolve some potassium permanganate in dilute sulphuric acid (appr. 1 mol/l)
and add powdered potassium metabisulfite in small amounts, until the liquid
is completely clear and colorless. Finally heat the liquid, until there is no
more smell of sulphur dioxide. The liquid, thus obtained, is a solution,
containing a fairly high concentration of Mn2+ and which is fairly acidic.
This liquid is called MN2.
Add some MN2 to a solution of potassium ferrocyanide: An off-white precipitate
is formed, the liquid becomes turbid like milk.
Add some MN2 to a solution of potassium ferricyanide: A dark brown precipitate
is formed. The precipitate is finely divided.