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Author: Subject: Tube Furnace Reactions
DFliyerz
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[*] posted on 12-5-2016 at 08:31
Tube Furnace Reactions


I recently acquired a tube furnace from someone here as well as 8' of quartz tubing from eBay. I was wondering, what are some interesting or useful reactions that can be done with a tube furnace?
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bob800
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[*] posted on 13-5-2016 at 07:07


Check out https://www.sciencemadness.org/whisper/viewthread.php?tid=10564 and https://www.sciencemadness.org/whisper/viewthread.php?tid=20124&goto=search&pid=248831
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JJay
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[*] posted on 13-5-2016 at 13:09


You can make aluminum chloride and metal hydrides in a tube furnace. They can be used for making ketones from carboxylic acids in a gas phase (see Vogel's ochem book for details).



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DFliyerz
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[*] posted on 13-5-2016 at 15:17


Additionally, for reactions between two gasses, how do you keep the flow rates to the correct proportions if you're generating the gases on-site?
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JJay
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[*] posted on 13-5-2016 at 15:48


That can be tricky... if the materials start as solids or liquids, you can prepare a solution of them in the correct ratios and vaporize it. Dealing with gases... you'd probably use a flow control valve or a venturi with metering... it could be very hard in an amateur setup.

[Edited on 14-5-2016 by JJay]




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blogfast25
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[*] posted on 13-5-2016 at 17:38


Quote: Originally posted by DFliyerz  
Additionally, for reactions between two gasses, how do you keep the flow rates to the correct proportions if you're generating the gases on-site?


That's virtually impossible.

But for most cases it isn't even desirable.

If you take a simple reaction:

A(g) + B(g) === > whatever

Then having either A or B in stoichiometric excess is usually good practice. In the next stage you'll separate the reaction product from any unreacted A or B.




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JJay
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[*] posted on 13-5-2016 at 18:14


Note that if you're vaporizing a solution of two reactants to produce gases in a particular ratio, you probably can't just boil the solution and hope for the best - you want to vaporize droplets or perhaps a slow trickle of reactants.



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careysub
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[*] posted on 13-5-2016 at 18:23


As blogfast observes, usually stoichometric mixtures aren't necessary or desirable for gas-phase reactions.

However, lets suppose that there is a case where it is. Since the reaction takes place at high temperatures I think we can assume the mixture is non-reactive at room temperature. In that case you could fill a pressure tank up some pressure with gas A, then add gas B to a calculated second pressure to get the correct mixture. Then you just open the valve to the tube furnace to feed in the correct reaction mixture.
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Magpie
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[*] posted on 13-5-2016 at 19:50


Feeding a gas at a known flowrate from a pressurized source can be done with a rotameter:

rotameter.png - 114kB




The single most important condition for a successful synthesis is good mixing - Nicodem
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JJay
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[*] posted on 14-5-2016 at 12:46


Quote: Originally posted by careysub  
As blogfast observes, usually stoichometric mixtures aren't necessary or desirable for gas-phase reactions.

However, lets suppose that there is a case where it is. Since the reaction takes place at high temperatures I think we can assume the mixture is non-reactive at room temperature. In that case you could fill a pressure tank up some pressure with gas A, then add gas B to a calculated second pressure to get the correct mixture. Then you just open the valve to the tube furnace to feed in the correct reaction mixture.


According to Ramsay's A System of Inorganic Chemistry, stoichiometric amounts of hydrogen and chlorine are desirable when producing hydrogen chloride by direct union of the elements. It's hard to imagine why anyone would want to do that... but I think it might be better to mix the gases at the tube entrance to deal with differing effusion rates. You could probably estimate the correct pressures to use with Graham's Law of Effusion, but the tank would only emit the correct reaction mixture for an instant.

[Edited on 14-5-2016 by JJay]




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