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Recrystsllization

Why recrystallization works on the basis that cooled solution is saturated with the desired material but not with the impurities?

Cuz I thought it is the desired material got crystallized, not the impurities?

Did I misunderstand something?

Thanks for any replies in advance :smile:

(edited 8 years ago)

Reply 1

MrFartFace

when you wash it through with a solvent, the desired product stays and the impurities dissolve with and you end up with the crystals and a bunch of solvent with the impurities dissolved in it.

Reply 2

alow

Original post by MrFartFace

when you wash it through with a solvent, the desired product stays and the impurities dissolve with and you end up with the crystals and a bunch of solvent with the impurities dissolved in it.

This thread is about recrystallisation, not washing on a filter...

Reply 3

mystreet091234

Original post by MrFartFace

when you wash it through with a solvent, the desired product stays and the impurities dissolve with and you end up with the crystals and a bunch of solvent with the impurities dissolved in it.

Then the solvent is saturated with impurities isn't it?

Reply 4

MrFartFace

Original post by mystreet091234

Then the solvent is saturated with impurities isn't it?

The solvent has all the impurities dissolved in it, the crystals shouldn't dissolve in the solvent, they stay in the funnel.

Reply 5

alow

Original post by MrFartFace

The solvent has all the impurities dissolved in it, the crystals shouldn't dissolve in the solvent, they stay in the funnel.

Have you ever done a recrystallisation? What you have said is completely wrong.

Reply 6

MrFartFace

Yeah I did the PSA in it earlier this year.

Reply 7

alow

Original post by MrFartFace

Yeah I did the PSA in it earlier this year.

Then you did it wrong. In a recryst you dissolve the crude product, filter out any insoluble impurities and cool the filtered solution to get your purified product, followed by drying.

Reply 8

MrFartFace

Original post by alow

Then you did it wrong. In a recryst you dissolve the crude product, filter out any insoluble impurities and cool the filtered solution to get your purified product, followed by drying.

Cheers for clearing that up.

Reply 9

mystreet091234

Original post by MrFartFace

The solvent has all the impurities dissolved in it, the crystals shouldn't dissolve in the solvent, they stay in the funnel.

Actually this is the question I was talking about.

I think D is weird as the solution should be saturated with soluble impurities, though I know ABC must be wrong.