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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: AlphaScent on December 03, 2013, 03:25:33 PM

Title: Rule of thumb for extractions
Post by: AlphaScent on December 03, 2013, 03:25:33 PM

So without getting into a great debate about partition coefficient and how smaller volume extractions are better then large volume ones;  I understand the math that is involved.

But practice is so much different than by the book.  What is your personal rule of them when doing an extraction?

Mine is 10% (ex. 10 mL of ether to 100 mL of aqueous material)

Title: Re: Rule of thumb for extractions
Post by: Doc Oc on December 03, 2013, 03:54:08 PM

I typically use more of a 1:1 ratio.  I do 1 extraction for pilot/exploratory reactions and 3 for something I'm actually trying to get isolated yield on.

Title: Re: Rule of thumb for extractions
Post by: Archer on December 03, 2013, 09:10:33 PM

I agree, one for crude based on what I am extracting and from what. And 3 for "best" conditions.  I usually determine the diminishing returns on aliquats of the extraction solvent if I am concerned (i.e. check each wash before combining them.

Ideal situation on pilot scale (100-500g product) is counter current extraction on a continuous process. Much lower solvent consumption.