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Topic: Fractional distillation questions  (Read 4438 times)

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Offline AlexCoste

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Fractional distillation questions
« on: March 02, 2016, 08:35:44 AM »
Hello,

i would like to setup a Fractional distillation appartus, but before i start i would be very grateful if you can help me on some questions

1) what would be the most appropriate ground glass joint size for distilling small quantity of organic solvents (approx ~100mL) ? 19/26, 24/29?

 2) i often read that vigreux column are not efficient for Fractional distillation because of their limited theorical plates, what would you advise me to use instead ? a liebig condenser with glass raschig rings ?

 3) what would be the ideal length for the fractionating column knowing that i would like to distill small quantity of solvents (approx 100mL)

that's all i wanted to know

thank you alot

Offline Babcock_Hall

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Re: Fractional distillation questions
« Reply #1 on: March 02, 2016, 10:26:32 AM »
What solvent are you trying to distill, and what is the impurity?

Offline AlexCoste

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Re: Fractional distillation questions
« Reply #2 on: March 02, 2016, 01:11:45 PM »
What solvent are you trying to distill, and what is the impurity?

thanks for the response Babcock, i would like to start with xylene, i would to distill other organic solvents too, all of them are pretty pure but i would like to purify them as much as possible
the impurities are not known

Offline Arkcon

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Re: Fractional distillation questions
« Reply #3 on: March 02, 2016, 01:57:04 PM »
1) what would be the most appropriate ground glass joint size for distilling small quantity of organic solvents (approx ~100mL) ? 19/26, 24/29?

I don't see how this is relevant.  The joint doesn't affect the distillation path.  Furthermore,joint size is only important for matching the separate pieces.  Do you have a variety?  Are you looking to purchase, and wondering what the difference is?  Those sorts of answers are needed from you for us to give useful answers.

Quote
2) i often read that vigreux column are not efficient for Fractional distillation because of their limited theorical plates, what would you advise me to use instead ? a liebig condenser with glass raschig rings ?

All are equivalent choices if we don't have the specifics.  What are you distilling (yes, I know xylene) what levels of what impurities do you want to remove,and to what standard do you want the purified product.  FWIW, the Vigreux column is perfectly adequate for simple mixtures, and Raschig rings are only needed for specialized applications.

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3) what would be the ideal length for the fractionating column knowing that i would like to distill small quantity of solvents (approx 100mL)

As above, it depends on what, specifically, you're doing.  You're going to have to explain why,in high school, you're trying to make the 'bestest' solvents, instead of just purchasing to the needs of your final application.
« Last Edit: March 02, 2016, 02:07:40 PM by Arkcon »
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline AlexCoste

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Re: Fractional distillation questions
« Reply #4 on: March 02, 2016, 02:57:50 PM »
thanks for your reply Arkon

1)a glassware with small joint size isn't more approriate for distilling small volume ? so you are saying that a 19/26 is as good as 29/32 for small volume?

2) i just want to make the solvent as pure as i can, the impurites are unkown to me
 i would like also to  isolate major components of essential oils

3) this is not a high school project, it's just a hobby but i thought it would belong best in the high school section, i apologize if i'm posting in the wrong section

Offline Arkcon

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Re: Fractional distillation questions
« Reply #5 on: March 02, 2016, 03:35:04 PM »
The bigger joint size is often associated with bigger flasks.  And a bigger flask means more loss when transferring.  Still, I don't know why you'd ask twice.  Would a 1 cup measuring cup hold a different amount of liquid than a 8 fl oz soda bottle?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline AlexCoste

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Re: Fractional distillation questions
« Reply #6 on: March 02, 2016, 06:05:34 PM »
The bigger joint size is often associated with bigger flasks. And a bigger flask means more loss when transferring.  Still, I don't know why you'd ask twice.  Would a 1 cup measuring cup hold a different amount of liquid than a 8 fl oz soda bottle?

that's why i asked what would be the most appropriate joint size.. to reduce loss when working with small volume



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