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miscible substances???


sirB!
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it has to be distillation as you will get some of the substance you want carried off with the boiling. although single stage distillation will work to a degree (which is pretty much just boiling it and collecting the vapour, although collecting the vapour is not necessary if you only want the less volatile substance.) multi stage distillation will give you a much better separation.

 

if the substances form an azeotrope then you cannot distill or boil through that temperature and there will not be separation. further separation would need to be achieved through other means.

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If there's a really big difference in boiling points you can do it by simple boiling. For example you can boil nearly all the water out of a dilute sulphuric acid solution (I don't recommend doing this at home).

 

(In practice, I know that sulphuric acid/ water forms an azeotrope)

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If you want the less volatile substance, as insane alien said, you can boil off the more volatile without a distiller. It would be somewhat wasteful, as some of the liquid you want to keep will also be boiled away. The longer you boil it, the more concentrated the less volatile liquid will be, but the more waste there will be.

 

If you want to keep the more volatile liquid, then you need a distiller. The classic example is water and alcohol. Repeating the distillation will increase the separation. However, they will not separate completely. In the case of alcohol, you can only get about 95% alcohol by distillation.

 

If you want to calculate how pure you can make it, you need to compare the vapor pressures at various temperatures and/or concentrations. It would help if you said what the two liquids were.

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partition coefficients only come into play when there is a two phase situation, ie. at least two components are imiscible in each other. what we are talking about here is a homogenous mixture.

 

ie, methanol and ethanol, water and ethanol, liquid N2 and liquid O2.

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