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Author: Subject: Flame while making sodium metaphosphate
Foeskes
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[*] posted on 6-7-2018 at 18:35
Flame while making sodium metaphosphate


I was trying to make sodium meta phosphate from NaH2PO4 by heating it in a old stainless steel crucible. After hearing for a bit it reached a temperature over 600°c judging from the cherry red color of the crucible. All of a sudden the smaller bubbles started to show up which makes a popping sound similar to hydrogen and some of the larger ones you can see a yellow sodium flame.
I quickly stopped and cooled down the mix. The result was a green colored(similar to FeCl2) glassy solid(Fe contamination).
What could the bubbles be. It seems to immediately stop after it is no longer is in contact with my torch.
I'm scared that it could be P4 or phosphine.

The crucible is old and it may have contamination of other metals(maybe even Aluminium or magnesium) from my older projects.
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walruslover69
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[*] posted on 6-7-2018 at 18:57


water is released in the conversion to meta phosphate. at temperatures that high the water will instantly turn to steam. It can be quite violent.
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Foeskes
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[*] posted on 6-7-2018 at 21:25


It still doesn't explain the visible flame though.
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wg48
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[*] posted on 7-7-2018 at 00:45


Quote: Originally posted by Foeskes  
It still doesn't explain the visible flame though.


I would think it was H2 burning yellow from contamination with Na. The H2 produced from the acid salt as it desolves the metal container or its metal contamination.

PS: If your not certain about what the gas is you should perform the experiment outside in the open or in a fumehood.

[Edited on 7-7-2018 by wg48]




Borosilicate glass:
Good temperature resistance and good thermal shock resistance but finite.
For normal, standard service typically 200-230°C, for short-term (minutes) service max 400°C
Maximum thermal shock resistance is 160°C
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unionised
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[*] posted on 7-7-2018 at 03:19


How did you not expect an acid to react with the steel?
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wg48
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[*] posted on 7-7-2018 at 05:16


Quote: Originally posted by unionised  
How did you not expect an acid to react with the steel?


and not just acid 600C molten acid salt !!!




Borosilicate glass:
Good temperature resistance and good thermal shock resistance but finite.
For normal, standard service typically 200-230°C, for short-term (minutes) service max 400°C
Maximum thermal shock resistance is 160°C
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