The maximal activation of phosphatase by MgSO4 was as great as the maximal by the activator found in Liebig''s beef extract. Small amounts of CaSO4, BeSO4, and ZnSO4 did not activate the enzyme appreciably. Zn poisoned the enzyme. The enzyme preparations used differed considerably in strength. Experiments were made to obtain highly active enzyme solution by adsorption on Al(OH)3 or kaolin and eluting with ammonia or secondary sodium phosphate. Kaolin adsorbed the enzyme at pH below 7, with ammonia for the elution. Neither adsorption nor elution was specific. The best adsorbent was Al(OH)3. Elution was difficult from this adsorbent with ammonia but was readily made with secondary sodium phosphate. The purest enzyme preparations were obtained by the last method. Even this did not appear to be quantitative. The activator was possibly MgSO4 but it is held that activation may be more complicated than the simple salt effect.