Will a long tube act like a fractionating column?

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Discussion Overview

The discussion revolves around the effectiveness of using a long tube as a fractionating column in a distillation apparatus, particularly in the context of avoiding rust from steel wool. Participants explore the principles of condensation and surface area in relation to distillation processes.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the assumption that a long tube would facilitate condensation without packing material, asking what would cause the gas to condense in the absence of steel wool.
  • Another participant emphasizes that a fractionating column requires a large surface area of a good thermal conductor to absorb heat from the gas, suggesting that without such a conductor, the gas would not condense.
  • A different viewpoint suggests that once the thermal conductor reaches the same temperature as the gas, the effectiveness of the fractionating column diminishes, and that insulation is typically used to maintain efficiency.
  • One participant expresses doubt about the effectiveness of a long tube alone, indicating that surface area is crucial for condensation.
  • Another participant humorously suggests unconventional packing materials for the reflux column while emphasizing the importance of keeping the condenser clean.
  • A later reply indicates that removing the steel wool and using a long tube does work as a fractionating column, sharing a personal experience.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of packing material in a fractionating column, with some arguing that a long tube alone may not be effective, while at least one participant claims success with the long tube approach. The discussion remains unresolved regarding the optimal design for effective distillation.

Contextual Notes

Participants discuss various assumptions about thermal conductivity, surface area, and the role of packing materials in distillation, but do not reach a consensus on the best approach or the underlying principles involved.

ShawnD
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I'm making a distillation apparatus and I've hit a block. The steel wool I packed into the plastic tubing (acting as a fractionating column) is rusting incredibly fast. I obviously don't want to be drinking rust, so can I just take the wool out and use an extra long tube instead? I'm thinking that having a tube that is very long will cause the gas to condense at least a few times along the way to add a few more theoretical plates. Am I right to assume this, or do I really need some kind of wool packed into this thing?
 
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I'm thinking...no. What makes you think that it would condense in the first place?
 
GCT said:
What makes you think that it would condense in the first place?
Why would it condense any less than when steel wool is there?
 
The point of a fractionating column is that you have a large surface area of a good thermal conductor to absorb the heat from the hot gas which causes it to condense. In the abscence of such a conductor, the gas will not lose heat, and thus will not condense
 
so-crates said:
The point of a fractionating column is that you have a large surface area of a good thermal conductor to absorb the heat from the hot gas which causes it to condense. In the abscence of such a conductor, the gas will not lose heat, and thus will not condense
But once the initial amount of gas heats the conductor to the same temperature as the gas, this no longer holds true. Fractionating columns make distillation a lot harder, so they're generally insulated anyway.
 
Well, I think surface area is key here, and with the column by itself, I don't think that it'll be effective...my humble opinion.
 
ShawnD said:
(snip) I obviously don't want to be drinking rust, (snip)
Are you talking reflux column or condenser? You do understand that you don't care (within limits) what washes back into the boiler. Pack the reflux column with old sweat socks. You don't want to pack the condenser --- that's where you collect the product --- try to keep that clean.
 
I had initially packed it at the end of the plastic tube (fractionating column) that is close to the copper tube (condenser). I guess that was a pretty stupid move. Packing at the end closer to the boiling pot would seem a lot more logical.

Thanks guys.
 
Just an update to this. I took the steel wool out and just went with the long tube. Using a long tube DOES work as a fractionating column.
Just thought you guys would like to know incase you ever make a still.
 

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