[Black_Forest]

Hi!
I have to run an experiment at elevated temperature in inert gas atmosphere, He.
Because He has a lower density than air  is he able to remove the air from the reactor?
Thank you!

[Borek]

Because He has a lower density than air  is he able to remove the air from the reactor?

No problems here, gases mix perfectly. Gravitational segregation at high temperatures (or even at room temperatures) is for (almost) all practical solutions neglectable.

Do you have to go for He? What about Ar?

[Donaldson Tan]

Helium is the ideal gas for heat transfer between nuclear reactors and steam turbine for electricity generation.

[Borek]

Helium is the ideal gas for heat transfer between nuclear reactors and steam turbine for electricity generation.

Original question doesn't mention nuclear reactor

[Dude]

It would help to supply the following:

1.  Is it just a chemical reaction in a 500 mL round bottom flask or is it more elaborate?

2.  Are you dealing with organolithiums or something extremely reactive or something that reacts with air, water or nitrogen at elevated temperatures?

3.  How hot is the reaction - will gases be evolved - does it have to be an open system?

If you have valves on the container, apply a vacuum, seal the container, and then bleed He into the container.  Repeat this three times and you are almost at 100 % He.

If you have an open system, let the He purge for 10-15 min before starting the reaction and keep a moderate flow (meaning you can displace the volume of the container in about 30 seconds - ie a 1 L container would need a flow rate of 2 L/min) of He exiting through a narrow orifice to make air diffusion back into the container minimal.

This is all relative.  If the material is extremely reactive you will have to resort to "Schlenk lines" or some ridiculously elaborate setup to get decent yields and to keep things safe.

[Black_Forest]

No problems here, gases mix perfectly. Gravitational segregation at high temperatures (or even at room temperatures) is for (almost) all practical solutions neglectable.

Do you have to go for He? What about Ar?

I was using Ar but my advisor want snow He.

[Black_Forest]

1.  Is it just a chemical reaction in a 500 mL round bottom flask or is it more elaborate?

I use an alumina container.

2.  Are you dealing with organolithiums or something extremely reactive or something that reacts with air, water or nitrogen at elevated temperatures?

I work with NaF and Kf at 1000C

3.  How hot is the reaction - will gases be evolved - does it have to be an open system?

it is not an open system. I use to wotk with a close system, I flash He and is going overpressure.


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