[johnj7]

Hello, i'm struggling with another extraction problem

The problem states:
"Data for solubility for 1 g of aspirin or salicylic acid:
Aspirin - 300 mL of H20, 17 mL of chloroform, 12 mL of ethyl ether
Salicylic acid - 460 mL of H20, 42 mL of chloroform, 3 mL of ethyl ether.

If you had a mixture of equal weights of aspirin and salicyclic acid, which solvent pair (ether-water) or (chloroform-water) would give the most efficient extraction.  Why?"

I orginally thought that the answer was ether-water.  I first calculated the partition coefficients for each solvent pair.  Then I saw that the ether-water partition coefficients were larger, and so thought that ether-water would give the most efficient extraction. 

However, the answer states:  "Chloroform-water.  Neither will be very good because both aspirin and salicylic acid will largely extract into the organic phases in all cases.  However, the chloroform-water system elaves mroe in the aqueous phase and thus allows a better separation.  A different means of purifying the compounds is needed." 

Could someone help me out/help understand what's going on?

Thanks

[Transmutation]

Or you could just convert the salicylic acid into aspirin with acetic anhydride and potassium carbonate.  Then could recrystallize pure aspirin. 

[ARGOS++]

Dear Johnj7;

Let’s give you the results first:
   In this particular case, your decision from your stomach is:     Right!
   In this particular case, the other argumentation is completely: Wrong!
   In this particular case, your own argumentation is also:          Wrong!   

How would you define “Efficiency” for such an Extraction?
    Hint:  Which Phase would you collect?

Recipe for visualisation:
With your new definition in mind, put 10.0 g ASA and 10.0 g SA together, and extract/calculate the Extraction following:  "Solubility Problem (Extraction!)”,  –   and be surprised!
 

Good Luck!
                    ARGOS⁺⁺

[agrobert]

Or you could just convert the salicylic acid into aspirin with acetic anhydride and potassium carbonate.  Then could recrystallize pure aspirin. 

How is this a separation?

[ARGOS++]

Dear Agrobert;

   How true!,  –    Maybe a young “Colt”.


Good Luck!
                    ARGOS⁺⁺

[minimal]

Or you could just convert the salicylic acid into aspirin with acetic anhydride and potassium carbonate.  Then could recrystallize pure aspirin. 

How is this a separation?

It's not, he was just making a joke, on the assumption you're separating in order to obtain the ASA.

[ARGOS++]

Dear Minimal;

I never interpreted it different, or as something else.


Good Luck!
                    ARGOS⁺⁺