EXTRACTION EQUILIBRIA OF BUTYRIC-ACID WITH ORGANIC-SOLVENTS

Fourteen solvents (five with a tertiary amine and different diluents, four C8-C18 alcohols, dibutylether, two hydrocarbons, and two vegetabl e oils) have been tested for the extraction of butyric acid. The highe st distribution coefficient for butyric acid is shown by solvents with tertiary amines. A ternary solvent with amine extractant, n-alkanes a s diluent, and higher alcohol as modifier can be advantageous in this procedure. Amines enable the extraction of acid at a pH above the pK(a ) value up to about pH 5.6. With an increase of the molecular weight o f alcohol, the value of the distribution coefficient decreases. Its va lue for pure alcohols is independent of the concentration of acid in t he aqueous phase. Equilibrium data suggest that the stoichiometry of t he acid-alcohol complex is 2:1, and only undissociated acid is extract ed.