[orgokid]

This seems like a fairly straightforward question but its been giving me some trouble

"Compund A has a room-temperature solubility of 20.2g/L in a certain solvent, while compund B has a solubility of 11.8g/L in the same solvetn and room temp. An extract from a plant contains 101 g of A and 5.9 g of B. How much A can in principle be crystallized in pure form from this mixture? Hint : How much solvent is required to dissolve this mixture? How much solvent is required to dissolve the amoun of B caontained in this mixture?"

Now i've calculated that it takes 5L to dissolve A with this solvent and 0.5L to dissolve B. SO would I need 5L or 5.5L to dissolve the mixture? I was assuming 5L...But even with that how do I calculate how A can be crystallized?

[Borek]

Treat both compounds independently - so you need 5L of solvent.

Now, imagine you have removed part of the solvent (by vaporization) - substance that is less soluble will crystalize, the other one will be left in the solution. How much solvent can you remove?

[corey2]

5 L to solubilize the whole mixture.

Make a slurry with 0.5L for 1h or so, then filter, and you obtain more or less 91g of pure A compound.

(In industrial preparations finding a solvent that will solubilize only the impurities is essential, you cannot do a chromatographical column over kilos or tons of products.  

[orgokid]

Alright I think I understand than. More understanding than calculations for this one. Thanks for all your help .