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Disposal of potassium permanganate and glycerol reaction

Submitted by sat on 09 August 2019

The reaction of potassium permanganate and glycerol:

This reaction is an example of a spontaneous exothermic reaction in which glycerol is oxidised to carbon dioxide and water (as steam) by potassium permanganate. The reaction may take some time to start, but as heat is produced the reaction speeds up, with the main reaction being:

14KMnO4(s) + 4C3H5(OH)3(l) ----> 7K2CO3(s) + 7Mn2O3(s) +5CO2(g) +16H2O(g) + heat

Other manganese species are thought to be produced in the reaction, such as Mn(VI) as green potassium manganate, and Mn(IV) as black manganese oxide.

As it is difficult to determine if there are unreacted chemicals present, we recommend quenching the reaction mixture with water.  This can be done by submerging the reaction vessel in a container of water (e.g. an ice cream container).

Given that you are not aware of the quantities of the reactants, if the water is coloured a deep pink it is likely that there is an excess of potassium permanganate. It is good practice to reduce the permanganate to a less reactive species, such as Mn(II) or Mn(IV).

Disposal of products if this has been conducted on a large-scale:

Reduce the manganese species to manganese dioxide and save for disposal by a chemical waste disposal contractor as follows:

Disposal of products if this has been conducted on a small scale and to clean the residue from reaction vessels:

Recommendations for conducting this activity:

If your school chooses to conduct this activity, we recommend using the method and scale available through the Royal Society of Chemistry1 for the following reasons:

Safety Notes:

References and further reading

1’Spontaneous exothermic reaction’, Royal Society of Chemistry website, http://www.rsc.org/learn-chemistry/resource/res00000742/spontaneous-exothermic-reaction?cmpid=CMP00005910 (September 2016)

Flinn Scientific. 2017. The Reaction of Potassium Permanganate with Glycerin. Flinn Scientific website, https://www.flinnsci.ca/api/library/Download/4ebf31df9511493db327d5d958512ef4