Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
-----------------
sodium sulfite : Na2SO3
sulphuric acid : H2SO4
calcium phosphate : Ca3(PO4)2
ammonium molybdate : (NH4)6Mo7O24 . 4H2O
Class:
------
elem=Mo,P
coordination
redox
Summary:
--------
Molybdates and phosphates produce a yellow complex in an anion, containing
both molybdenum and phosphorus. This complex is slowly reduced by sulfite.
Description:
------------
Add some solid ammonium molybdate to dilute sulfuric acid (10% by weight):
The solid slowly dissolves, the liquid becomes clear and colorless.
Add some solid calcium phosphate: The liquid becomes yellow and turbid. Part
of the phosphate dissolves. A phosphate-molybdate complex is formed, which
causes the strong yellow color. A precipitate remains, this may also be due
to formation of CaSO4.
Add some solid sodium sulfite: The solid dissolves and the yellow color
becomes even more intense. After a while, the color shifts towards green and
finally the liquid turns blue/green, with a yellow/green precipitate.