Extractions

[jgalt42]

So we know that differential solubilities govern extractions

Does that mean that when you have a strong acid present, the best extractor is if you pair it up with a weak base? Similarly, if you have a weak acid, the best extractor is if you pair it up with a strong base?

Also does the converse of these statements apply? It's pretty much the same thing.

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[mcloaf]

The "best" extractor is going to depend on what it is you're trying to separate. You'd need to look at the relevant pKa's and make a determination based on that for an acid-base extraction.

 

[jgalt42]

When comparing Pka's what exactly are you looking for? Is the solution that has the greatest difference of Pka with the solute that you are trying to extract the best extractor?

 

[MedPR]

When comparing Pka's what exactly are you looking for? Is the solution that has the greatest difference of Pka with the solute that you are trying to extract the best extractor?

If you are trying to extract something from a solution based on pKa (as opposed to solubility) you want a column that will readily react with whatever you are trying to extract from your solution. What you want will depend on what you are trying to extract.

 

[theseeker4]

When comparing Pka's what exactly are you looking for? Is the solution that has the greatest difference of Pka with the solute that you are trying to extract the best extractor?

If you are extracting a compound from an aqueous solution, you need the solution to be at a pH where the compound is neutral. If it is positive or negative, it will prefer to stay in the aqueous layer. If you are extracting a compound from an organic solution (into water) you want the pH of the water to be where the compound is charged.

 

[cfive22]

So we know that differential solubilities govern extractions

Does that mean that when you have a strong acid present, the best extractor is if you pair it up with a weak base? Similarly, if you have a weak acid, the best extractor is if you pair it up with a strong base?

Also does the converse of these statements apply? It's pretty much the same thing.

In order to separate different components through extraction, you need to have an idea of what you're separating. If you're separating a strong acid from a weak acid and strong base, you'd need to use a weak base to ensure that only the strong acid gets into the aqueous layer. Then you can use a stronger base to extract the weak acid and so on and so forth.