The Na salt is dissolved in the smallest volume of H2O, a saturated solution of aqueous NaCl/Et2O is added and the mixture is stored at 0o for 24hours. Then shake the mixture well, keep it in the cold for another day and filter the crystals with gentle shaking, wash them with ice-cold saturated aqueous NaCl saturated with Et2O, dry them over CaCl2 and extract them with absolute EtOH. Add ~10mL of H2O to the solid followed by enough Et2O to incipient cloudiness. Store it overnight at 0o. Add ice-cold Et2O to make 250mL, collect the crystals, wash them with Et2O then pet ether and dry them in air. The purification can be repeated with NaCl and Et2O with ~85% recovery. NB: precipitation will not occur unless enough H2O is present. Its solubility in H2O is 10%. [Cortese J Am Chem Soc 59 2532 1937.] The free acid has m 141-144o. [Norman Ark Kemi 8 331 1956.] It forms mixed micelles and solubilises some membrane proteins [Hajjar et al. J Biol Chem 2 5 8 192 1983]. [Beilstein 10 IV 1611.]
