PowerLabs Sodium Peroxide Deflagrations

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Introduction:

  Sodium Peroxide is said to "ignite and/or explode in contact with organic matter or readily oxidizable substances" (Merck Index 12th ed.). The commercial product, 90 - 95% pure Na2O2, has a variety of very important uses as a bleach and as a CO2 => O2 converter in submarines, diving bells, air purifiers, etc. It is one of the most expensive reagents stored by PowerLabs, more expensive then Silver Nitrate for example (over one dollar/gram), but the prospect of watching something "ignite or explode in contact" was just too tempting to pass on...
 

Materials:

 A 25 gram bottle of Sodium Peroxide Analytical Grade (96%) was used up in a series of experiments, some of which are reported here.
 The beaker used for this experiment was a Schott Duran beaker, tougher than Pyrex. Other reagents used are in Bold on the paragraphs below:

 

Procedures:

   NOTE: The procedures described below are EXTREMELY hazardous and should NEVER be attempted. These experiments are outlined for informational purposes ONLY.
   Sodium Peroxide decomposes very quickly in water as it first forms concentrated Hydrogen Peroxide and Sodium Hydroxide and then the H2O2 is decomposed by the high PH of the caustic solution generating large amounts of Oxygen gas. Calcium Carbide is also decomposed in water, forming Calcium Carbonate and Acetylene Gas... Acetylene Gas combusts explosively in a pure Oxygen atmosphere. It also decomposes spontaneously above 15PSI. A small sample of Sodium Peroxide was first mixed with Calcium carbide and water was added. A flame was held above the reading mixture and this produced a roaring, exploding oxy-acetylene flame. A second sample was remotely mixed inside a corked flask and this gave rise to a violent explosion after a brief delay during which pressure built up.
   Secondly a simple deflagrant was attempted, this one a modified flash powder mixture employing Magnesium powder, Sulfur and Sodium peroxide as the oxidizer. The first problem with using Na2O2 as a solid oxidizer is that it comes in the form of spheres maybe 1mm in diameter; these have a relatively large surface area which translates into a slow decomposition rate and thus poor fuel/oxygen balance and slow combustion rates for the deflagrant. Pulverizing the peroxide proved very difficult as the spheres are very tough. This hygroscopic, water decomposed chemical will be rendered inert much quicker in that form. A finer form was obtained after much work with a mortar and pestle. This was added to the solid fuels, and mixing was started by rolling a small amount in the middle of a sheet of paper. Within seconds the material became clumped and ignited, deflagrating very violently and burning the work table it was being mixed over. Sodium Peroxide is most certainly not a good solid fuel candidate for deflagrants!
  Mixing Sodium Peroxide with warm Ethylene Glycol resulted in a violent explosion and ensuing fireball that splattered burning EG everywhere.

  The "classic" Sodium Peroxide demo is to pour some sodium peroxide on top of a few sheets of paper and drop water on it. As the water decomposes the Na2O2 Oxygen is produced. The Na2O2 also reacts directly with the paper oxidizing it very rapidly. The heat produced ignites the paper which burns in a pure oxygen atmosphere, producing a very violent, hot, bright flame with the characteristic Sodium yellow spectra. In this particular demo one teaspoon of Na2O2 was used for 4 sheets of toilet paper stuffed in a glass beaker.
 

Results:

 A flame erupts as sodium peroxide provides paper with the heat and the oxygen it needs to ignite and burn fiercely.  Just a few seconds after the water soaks through the paper into the sodium peroxide the beaker spontaneously erupts into a violent, roaring/crackling flame that reaches over a few feet in height and is hot enough to quickly melt through the bottom of the beaker. I suspect that part of the reason why the beaker melted must have been due to chemical attack from molten sodium peroxide at 675C, as evidenced by severe corrosion on the inside after the flame extinguished itself. The beaker becomes so hot during this experiment that the table it is sitting on spontaneously ignites also!
 Click on the image to download the 4.4MB, .mpg Video of the reaction.
 

Relevant Links:

PowerLabs Potassium Permanganate Hypergol; another fine example of hypergolic reactions!
PowerLabs Deflagrants overview; examples of similar reactions to the one on this page.

 
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