Specificity: Human Acid Phosphatase. The reagents were evaluated for potency, purity and specificity using most or all of the following techniques: immunoelectrophoresis, cross-immunoelectrophoresis, single radial immunodiffusion (Ouchterlony), block titration, ELISA, immunoblotting and enzyme inhibition. Cross-reactivity Cross-reactivities against enzymes of other sources may occur but have not been determined.