guy
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Is teflon resistant against molten NaHSO4?
I'm going to make NaHSO4 by heating ammonium sulfate and sodium sulfate together. I want to make a thin layer so Im thinking about using a teflon pan.
The question is, will teflon resist attack from molten bisulfate?
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chemoleo
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Teflon is used under extremely harsh conditions, magnetic stirbars, reactors, microwaves, conc nitric acid, god knows what. The only thing that could
damage it is high temperature. I'd check out at what temp Teflon decomposes, and keep this reaction well below it! Why not using glass? Is it attacked
by bisulfate? That'd be news to me!
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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guy
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| Quote: | Originally posted by chemoleo
Teflon is used under extremely harsh conditions, magnetic stirbars, reactors, microwaves, conc nitric acid, god knows what. The only thing that could
damage it is high temperature. I'd check out at what temp Teflon decomposes, and keep this reaction well below it! Why not using glass? Is it attacked
by bisulfate? That'd be news to me! |
Because I don't have any glassware thats like a pan so I can spread the mixture out.
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solo
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use a pyrex pie pan or a pyrex cake mold..................solo
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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not_important
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I'm seconding solo - teflon starts degrading at around 280 C, really cutting loose at 350 C or so. The first temperature is in the range of ammonium
sulfate's melting temperature (it's not a nice sharp melting point, depends on heating rate and other things). Sodium bisulfate melts at around 310 to
320, as it melts it forms the pyrosulfate which may have a yet higher melting point.
The teflon can deal with the sulfate chemically, it's just that the process runs at temperatures where thermal decomposition is a concern.
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guy
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| Quote: | Originally posted by solo
use a pyrex pie pan or a pyrex cake mold..................solo |
The pyrex pie pan works fine during the heating but after turning off the heat, while it cooled down, it broke into serveral pieces. Is this my fault
or the pan's fault?
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evil_lurker
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Probably a little bit of both.
I recommend using pyrex pan as well, but next run try putting it in a pre-warmed oven and letting it cool very slowly over a period of several hours.
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chemoleo
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The fault is like the formation of tough long crystals which break the pan because of expansion. I've seen this elsewhere, letting a salt melt cool in
glass often gives breakage upon cooling (i.e. the crystals take up more space than the molten mix). The trick is to empty the pan/tube into a
different container and let it cool there. The residue in the pan/tube can then be scratched out.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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not_important
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It also happens when the freezing melt glues itself well to the glass, and then continues to contract. Thin layers usually avoid the problem; or, as
chemoloe said, pouring the melt out onto a cold surface (iron plate - not with acids - or flat stone) to flash cool it and only leave a very thin
layer in the container.
Edited to say - slow cooling might have helped in this case, cookware is usually fairly thick, too fast of cooling can set up strains even in
borosilicate glass.
[Edited on 25-9-2006 by not_important]
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guy
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Wow ok that makes perfect sense. Now to buy another pan. Its going to be hard to pur it into another pan, so would clumping it into a small area and
moving it around so it doesn't stick work?
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not_important
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It could - thin layers usually don't cause problems because they don't have enough bulk to exert any strength. But it will be pretty hot and getting
hard, pushing it about might be difficult.
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