4.1 REACTIVE EXTRACTION
DESCRIPTION
A simple reaction, followed by isolation of the desired product from the solution, will give a example of a typical application of extraction.
Few organic acids are liquid and soluble in water. Sodium salts of carbon organic acids are ionic compounds that are also very soluble in water. If an aqueous solution of one such salt is acidified with a strong mineral acid, the much weaker organic acid is produced.
Weak organic acid is largely un-ionized in the aqueous solution.
No change is observed when the reaction is carried out because the solutions of the starting materials and the products are colorless. The organic acid is soluble in water and thus, does not separate. It is necessary to extract the propionic acid from the aqueous solution with solvent. The solvent solution must be dried to remove residual water, following which
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Dissolve the salt in 120 ml of tap water. Add 60 ml 6 M Hcl and stir the mixture with a glass rod.
Add 24 g solid Nacl to the solution and stir the mixture for about 2 minutes.
Support a 500 ml separatory funnel on a ring, close stopcock and then a clean beaker is placed beneath the exit tube. Transfer the aqueous solution from the beaker to the separatory funnel. Do not transfer any un-dissolved sodium chloride in the beaker to the funnel.
Extract the aqueous solution with selected solvent in the following manner:
a) Add 40 ml of solvent to the solution in the separatory funnel.
b) Place the plastic stopper in the neck of the funnel. Shake
c) Slowly remove the lower aqueous layer through the stopcock into the same 500 ml beaker in which the solution is there.
d) Pour the upper solvent layer through the neck of the funnel into a clean 125 ml Erlenmeyer flask.
Return the aqueous solution from the 500 ml beaker to the separatory funnel. Add another fresh 40 ml of solvent to the funnel and again extract the aqueous solution as you did in b)