Is the Flask Closed or Open to Atmosphere During Reflux Heating?

[Rajini]

Hello All,
I have a doubt in reflux apparatus. Usually when we heat some solvents in a glass flask it may evaporate..and this vapour is cooled by reflux condensor and again go into boiling solvent. So on heating the amount of solvent won't decrease or decompose. What I want to know is whether the flask is closed or left open to atmosphere while heating?
Regards, Rajini.

 

[Bystander]

the flask is closed or left open to atmosphere while heating?

Ordinarily, NOT ALWAYS.

 

[ManiacaLaugh]

It is very seldom a good idea to heat a completely sealed apparatus, as pressure can build up and cause it to explode. If your reactants are water sensitive, a drying tube can be placed on top of the condenser to eliminate moisture, and if they are oxygen sensitive the apparatus would need to have a stream of inert gas supplied, or be run inside a glove box.

 

[Rajini]

Hello Bystander,ManiacaLaugh,
Thanks for your reply. My reactants are oxygen sensitive. Also I cannot heat inside a glovebox/bag! So plan to pass continuously an inert gas (Ar) while heating (30 to 60 min of heating around 250 celsius is enough for my case).
Regards, Rajini.

 

[Borek]

So plan to pass continuously an inert gas

Depending on how sensitive your reactants are, you may want to use an oxygen scrubber with vanadium(II) chloride solution.