Re: Is there a negative catalyst for manganese dioxide ?

Dear Loz,

This is a really good question!  As far as I have been able to ascertain, 
there is no simple “quenching” agent for manganese dioxide decomposition 
of hydrogen peroxide.
It would appear that we need to turn this problem on its head and use a 
faster reaction to use up all of the H2O2 rapidly.  Then from the 
byproducts, you can indirectly determine the amount of H2O2 that had to 
have been present in the original sample.

As a first attempt, why not try using a known excess of iodide ion.  The 
H2O2 will rapidly oxidize the I- ion to triiodide, I3-, which can then be 
determined by back titration with sodium thiosulfate.  The MnO2 will also 
react with the excess I3-, but is should be a stoichiometric reaction, not 
a catalytic one.  It will be necessary for you to accurately and 
reproducibly add the same amount of MnO2 to each sample.

There do not appear to be very many web-based discussions on iodometry, 
but here is a site that describes an analysis very similar to what you 
want, except they are analyzing for Vitamin C.   http://buffer.bu.edu/quantlab/1998-Fall/exp6.html

A trip to the library is definitely justified for some background 
material.  I would suggest that you look at any sophomore quantitative 
analysis text.  The one that I happened to have on my desk is Quantitative 
Chemical Analysis 2nd Ed., D.C. Harris, published by Freeman in 1987.  
However, any good collegiate text will have chapters on electrochemistry 
and redox titrations.

This is a good set of experiments.  Good Luck!!


Dr. Michael M. Gallagher
Senior Research Chemist
J.R. Simplot Co.