Will a long tube act like a fractionating column?

In summary, the conversation discusses the use of a distillation apparatus and the issue of rusting steel wool. The individual is questioning whether they can use a longer tube instead of the steel wool to increase the effectiveness of the fractionating column. However, there is a debate about whether a longer tube will actually cause the gas to condense more effectively, as the point of a fractionating column is to have a large surface area of a good thermal conductor. It is also mentioned that the purpose of a fractionating column is to make distillation more difficult and it is usually insulated. The conversation concludes with the individual updating that they have successfully used a longer tube as a fractionating column.
  • #1
ShawnD
Science Advisor
718
2
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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  • #2
I'm thinking...no. What makes you think that it would condense in the first place?
 
  • #3
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?
 
  • #4
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
 
  • #5
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.
 
  • #6
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.
 
  • #7
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.
 
  • #8
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.
 
  • #9
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.
 

1. How does a long tube act like a fractionating column?

A long tube acts like a fractionating column by separating a mixture of liquids based on their boiling points. The longer the tube, the more efficient the separation process will be.

2. What are the benefits of using a long tube as a fractionating column?

The main benefit of using a long tube as a fractionating column is that it allows for more precise separation of liquids with similar boiling points. It also allows for greater control over the separation process.

3. Is a long tube always necessary for fractionation?

No, a long tube is not always necessary for fractionation. It depends on the mixture being separated and the desired level of separation. In some cases, a shorter tube or other separation techniques may be more suitable.

4. How does the temperature of the long tube affect the separation process?

The temperature of the long tube plays a crucial role in the separation process. The tube is heated at the bottom, and as the vapors rise, they condense at different levels based on their boiling points. The temperature gradient along the tube allows for the separation of different components.

5. Are there any limitations to using a long tube as a fractionating column?

One limitation of using a long tube as a fractionating column is that it can only separate liquids with boiling points that differ by at least 30 degrees Celsius. Additionally, the process may be time-consuming and may require precise control of temperature and flow rates.

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