metalresearcher
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Burning speed of KNO3
'Burning' means actually burning *by* KNO3 as the latter does not actually burn, but the fuel burns.
What I tried was KNO3 + sugar. Plain as I bought it (via ebay) mixed with sugar on a 65:35 ratio I got the following conclusions:
- mixed in a heap: it cannot sustain itself I need a burner to sustain combustion.
- mixture in a steel tube (and a little sulfur added) does sustain combustion
- KNO3 grinded with a mortar + pestle resulted in a much faster combustion sustaining itself.
- Adding some (15-20 parts) CaCl2 slowed down combustion but colored the flame brick red but not as nice when using KClO3 as an oxidizer.
Any ideas ? The best way for me to get a red flame is KClO3 + sugar + a bit CaCl2 (the orange red mixed with the purplish K color results in red).
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Adas
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Very good red colorant is Sr(NO3)2, you can try it
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Formatik
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My guess is the reaction stoichiometry is:
5 C12H22O11 + 48 KNO3 = 24 K2CO3 + 36 CO2 + 55 H2O + 24 N2
This corresponds to a mass ratio of 2.84 to 1 for KNO3 to sugar. I recently used a ratio of 3.5:1 and got a decent burn.
The ratio you've used is 1.86 to 1. This ratio is close to the smoke bomb ratios I've seen 1.5-1.66 to 1 (here). Carefully carmelizing like seen there creates a more intimate mixture.
The ingredients should always be fine as possible. Use e.g. an electric blender to grind the sugar.
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Neil
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If you have not already looked at the data Richard Nakka has up, you may find it illuminating.
http://www.nakka-rocketry.net/sucrose.html
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metalresearcher
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Tried the 2.84 : 1 which is even worse. I burnt 0.7 g sugar + 2 g KNO3 which I had to keep ignited with the burner while my fumehood completelyfilled
with smoke  .
I got the 65:35 ratio from several sites describing "rocket candy" which uses this ratio.
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Neil
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maybe you need to purify your KNO3?
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metalresearcher
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This KNO3 from ebay is rather pure.
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Neil
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and fire resistant? 
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Steve_hi
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Can you do this sugar burn with Nh4No3 if so what would be a proper ratio I did try it with icing sugar but it only melted so Ive been thinking it
doesnt burn like potassium nitrate does but maybe i haven't mixed it right
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hissingnoise
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There's a section on ammonpulver in COPAE in the site library.
Mixed with say, charcoal, NH<sub>4</sub>NO<sub>3</sub> gives a propellant similar to smokeless powder.
It needs a strong igniter . . .
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Steve_hi
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How does one acess the site library?
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hissingnoise
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One goes here http://sciencemadness.org/
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metalresearcher
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I did it now with Al powder (600 mesh from ebay)
2 KNO3 + 4 Al + S -> 2 Al2O3 _ K2S + N2
in this ratio: 1 g KNO3 (grinded) + 0.5 g Al + 0.15g S resulted in a fast and very blinding white flash !
That is why this is called 'flash powder'.
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