Fluorite
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High Boiling Solvents for HCl Synthesis to Prevent Flask Cracking
Hello Sciencemadness Community,
I’m trying to produce HCl gas by reacting sodium bisulfate with table salt in an Erlenmeyer flask, followed by distillation. My concern is about the
flask potentially cracking due to salt expansion.
To address this, I am looking into using high boiling solvents as part of the process. The challenge is to find a solvent that is inert to HCl and can
withstand the reaction conditions. would candle wax or ethylene glycol or glycerol work for this?
Does anyone have suggestions for suitable high boiling solvents for this purpose? Additionally, any advice on safety measures or best practices for
this synthesis would be greatly appreciated.
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Kloberth
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You do not need to worry about salt axpansion in that case. Only if you melt some salt then let it solidify in a flast and remelt it the expansion can
become a problem not when heating two powdered salts.
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woelen
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Do you want to make dry HCl, or hydrochloric acid?
Standard sodium bisulfate, as you can buy for swimming pools pH-minus, or for cleaning purposes, is NaHSO4.H2O. On heating, this loses water vapor at
fairly low temperature (not much above 100 C). When NaCl is mixed with this hydrated NaHSO4, then you get a mix of water vapor and HCl. If you want
dry HCl, then you first need to heat the NaHSO4 quite strongly, to drive off all water, and then use this dried material with dry NaCl to get HCl.
Getting HCl from this dry mix, however, requires much stronger heating and I doubt whether glass is suitable at all for this process.
[Edited on 12-1-24 by woelen]
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teodor
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Thermal decomposition of MgCl2 hydrate to MgOHCl occurs at 235C which on heating gives dry HCl below 415C. So, you can try this if you have problems
with the salt expansion. But also you can mix the salts with quartz sand, it could prevent cracking of glass, but try with some inexpensive glassware
first.
For MgCl2 route check this thread:
https://www.sciencemadness.org/talk/viewthread.php?tid=15142...
Also, I don't see why paraffin oil can not be used as a reaction medium, it should be inert both to SO3 and HCl. I think you have to try.
Also you asked about safety.
HCl can do quite a big damage, keep all expensive things far away also be prepared that all metal things nearby will corrode. It is quite impossible
to handle HCl in an average laboratiry without leaks, you will notice that. So keep all metal parts far away.
[Edited on 12-1-2024 by teodor]
You can try NH4Cl as an alternative to NaCl in your sulfate process. Probably it could lower a bit a reaction temperature.
Commercial NaHSO4 hydrate can be of varying composition with a different H2SO4 percent, I can imagine this can change the reaction conditions a lot.
[Edited on 12-1-2024 by teodor]
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