Decomposition of hydrogen peroxide by sodium nitroprusside

Summary

The photochemical after-effect in the reaction between hydrogen peroxide and sodium nitroprusside is due to the photo-formation of sodium aquopentacyanoferrate. The formation of aquopentacyanoferrate in pre-insolated nitroprusside solution has been proved by qualitative tests. Colloidal Prussian blue does not cause the after-effect.

Pre-insolated nitroprusside continues to react in the dark in the manner indicated by the after-effect. Addition of ferrocyanide causes the reduction of aquopentacyanoferrate to aquopentacyanoferrite, which decomposes hydrogen peroxide with a high velocity. The validity of the suggested mechanism for the after reaction has been tested by the effect of potassium cyanide and sodium nitrite, which have been shown to suppress the after-effect by converting aquopentacyanoferrate to ferrocyanide and nitroprusside respectively. Sodium aquopentacyanoferrate, prepared in the laboratory and added to hydrogen peroxide-uninsolated nitroprusside mixture in the dark in presence and absence of ferrocyanide, has been shown to reproduce the observations obtained by insolation.