Distillation

[MedPR]

I'm reading TBR and it says "The vapor collides with the inner walls of the distilling column, where it condenses. Some of the condensed liquid drips into the distilling flask and some reevaporates"

I don't understand... You heat up the solution and the more volatile solvent turns into gas and rises up into the distilling column. That's fine.

Here's where I get confused. So this vapor created by boiling rises up into the distilling column and either condenses or reevaporates. Does the vapor that condenses drip back down into the original part of the system that is being heated?
How does a gas re-evaporate?

---

Members don't see this ad.

 

[chiddler]

yes this is called fractional distillation. i referred to it in an earlier post today. the idea is to increase surface area by just putting some material for the vapor to bind to. this gives opportunity for the less volatile vapor to get stuck on this material to purify the vapor with more of the more volatile vapor.

once it sticks to the material, it can drip back down into the solution, or it can reevaporate. but either way, you effectively slowed down the less volatile vapor.

 

[SaintJude]

So is the substance that drips down the receiving flask first the lower-boiling point component... the more volatile vapor?

 

[chiddler]

So is the substance that drips down the receiving flask first the lower-boiling point component... the more volatile vapor?

the less volatile. because it condenses more easily than the more volatile when in contact with a surface.

 

[SaintJude]

If it has a lower boiling point isn't it then the more volatile vapor?

 

[chiddler]

If it has a lower boiling point isn't it then the more volatile vapor?

yes. lower BP means it stays in gase phase more easily. so it will not condense as much.

 

[SaintJude]

More volatile = lower bp. Which is the compound typically to enter collecting flask first.

[FONT=Arial, Helvetica, sans-serif]The more volatile liquid (the liquid with the lower boiling point) will typically evaporate first and the vapor will pass into a condensing column, where it can revert into a liquid (condense) on the cool glass where it trickles into a collection flask. .

[FONT=Arial, Helvetica, sans-serif]
From: http://www.chemhelper.com/distillation.html


.

 

[chiddler]

More volatile = lower bp. Which is the compound typically to enter collecting flask first.

[FONT=Arial, Helvetica, sans-serif]
From: http://www.chemhelper.com/distillation.html


.

yes. not talking about the collecting flask, just the prior mentioned "extra material".

but you were. sorry i missed that.

 

[SaintJude]

oh, no sorry, my bad.