Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
-----------------
hydrochloric acid : HCl
sodium sulfide : Na2S . 3H2O
potassium hexa nitrito cobaltate (III) : K3 [Co(NO2)6] . H2O
Class:
------
elem=Co,S,N
redox
Summary:
--------
The hexanitrite cobaltate (III) ion is strongly affected by sulfide. A black
compound is formed. On acidification of this, remarkably, no hydrogen
sulfide is formed. Probably the black compound is a compound containing
sulfide and nitrite in a single compound, which on acidification results
in oxidation of the sulfide.
Description:
------------
Add some solid cobalt yellow to a solution of sodium sulfide: The solid becomes
black at once.
Add some concentrated hydrochloric acid (appr. 30% HCl by weight): A gas is
evolved violently. The temperature does not rise noticeably. The gas mixture
above the liquid becomes light brown. The black solid does not dissolve
completely. There is no strong smell of hydrogen sulfide.