woelen
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Experiments with Na2O2: extreme water-sensitivity
I received my 800 grams of Na2O2 and did some experiments with this. The Na2O2 is a very fine powder with a pale yellow/beige color. I already had
some other Na2O2, in the form of small very hard prills, nearly impossible to crunch. That other Na2O2 is only moderately reactive. The stuff I have
now is amazingly reactive.
My original intent is to keep most of it in stock as an alternative supply for H2O2, which can be stored indefinitely. I separated 30 grams or so from
the lot in a small bottle and packaged my main stock very well.
I mixed a small spatula of the Na2O2 with a similar amount of powdered sulphur. This mix can easily be ignited. It is not very friction-sensive, even
when scratched and ground with a sharp metal screwdriver it does not ignite. But most amazing is that addition of a small drop of water makes the
stuff go "whoosh" immediately.
I did a similar experiment with powdered sugar and had the same observation. A small drop of cold water causes immediate ignition of the mix.
Next, I decided to check its sensitivity with red P. Again, the mix is not easily ignited by scratching or hitting. I did not manage to ignite the mix
by hitting or grinding it with the screwdriver or with a round glass stick. Addition of a drop of water leads to explosion. A fairly loud THUMP sound
is produced when a drop of water is added. It sounds like a deep bass from a big speaker.
Finally, I tried Na2O2 with 99.9% Zn3P2, which is flammable and a very strong reductor. With this chemical, the reaction is comparable to the reaction
with red P. White smoke is produced and a loud THUMP noise is produced when the mix is ignited with water. Pressure and grinding do not lead to
ignition.
Na2O2 is not useful for pyrotechnic purposes, due to the extreme sensitivity of mixes with this chemical to water. I think that a small amount of
water leads to formation of pure H2O2, which immediately ignites combustible materials. The reaction between Na2O2 and water also is quite exothermic
and the heat produced in this reaction of course also helps igniting the mix.
When Na2O2 is added to water, then indeed quite some hydrogen peroxide is formed. The reaction proceeds quickly and completely and must be carried out
slowly if a very fine powder is used.
Also very interesting is the reaction of Na2O2 with a dilute acidified solution of K2Cr2O7. When this orange solution is poured over a small amount of
powdered Na2O2 on a glass surface, then beautiful deep blue streaks of CrO5 are produced. This forms an impressive wave pattern with the yellow/orange
solution of K2Cr2O7. The effect only lasts for a short time. CrO5 is not very stable in aqueous solution and quckly decomposes to chromium(III) and
oxygen.
Finally, I sprinkled some Na2O2 over toilet paper and put this in a glass beaker, folding the paper into a very loose "ball". I sprayed a small amount
of water over the paper, such that the water slowly moisturizes the paper. At a certain moment the paper suddenly ignites with a violent flame (much
more violent than normal fire). So much heat is produced in this fire, that it leads to quick cracking of the glass beaker!
For all experiments I only used 50 mg at most of Na2O2, except for the last experiment in which I think I used half a gram or so.
Do these experiments on a concrete floor, where nothing flammable is nearby. Zn3P2 is very toxic, avoid inhaling dust. In the experiment, however, all
of the phosphide is destroyed and no particularly toxic waste is produced.
[Edited on 10-4-17 by woelen]
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tsathoggua1
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Just an observation-owing to the violence reported during this reaction, and extremity of its sensitivity towards water in mixtures with potential
fuels, stirring with a glass rod strikes me as a bad idea, because of the risk of shrapnel.
And especially with phosphorus-based mixtures, that just strikes me as a composition that is likely to be particularly dangerous, just remember what
Armstrong's mixture is like. I should think this an even stronger oxidizer than chlorates.
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woelen
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Yes, these mixtures are very dangerous and should NEVER be applied in actual pyrotechnic displays/devices. As I wrote in my post, I only used 50 mg or
so quantities and then the risk is low if you use long sticks, wear glasses, and have your face at appr. 1 meter distance of the mixes. The
experiments should NOT be scaled up.
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