Small amounts of  acetic acid were removed by shaking with small portions of 2M  NaOH until the aqueous phase  remained faintly alkaline.  The  sample, after washing with water, was  dried with anhydrous Na₂SO₄, and did  through a modified Vigreux column .  An  additional purification  step  is  fractional crystn from  the  liquid. Alternatively, there is less loss of  acetylacetone if  it is dissolved in four volumes of benzene and the soln is shaken three times with an  equal volume of distd water (to extract acetic acid): the  benzene  is then removed by distn.  at 43-53 °C and 20-30mm through a helices-packed column. It is  then  refluxed over P₂O₅ (10g/L) and fractionally distd under reduced pressure.  The distillate (sp conductivity 4 ×10^-8 ohm^-1crn^-1)  was suitable for polarography. To recover used Acetylacetone (CAS NO.), metal ions were stripped (1:10) from the soln at pH  1 (using  100mL 0.1M H₂SO₄/L of  acetylacetone). The acetylacetone was washed with (1:10) ammonia soln (100mL/L) and with distd water (100mL/L,  twice), then treated as above. It complexes with Al, Be, Ca, Cd, Ce,  Cu, Fe²⁺, Fe³⁺, Mn, Mg, Ni, Pb and Zn.