1. Sodium salicylate modifies the precipitation of normal rabbit serum protein by sodium tungstate, and partially inhibits the precipitation of horse serum euglobulin by rabbit antiserum. Sodium salicylate added to a system containing crystalline egg albumin and its antibody partly prevents the formation of precipitate, the degree of inhibition being related to the concentration of salicylate.
2. Precipitation in the equivalence zone is more readily prevented by salicylate than precipitation in the region of antibody excess, the immune system becoming progressively less sensitive to the action of salicylate as the excess of antibody becomes larger.
3. Formed precipitates were partly dissolved following resuspension in the presence of salicylate.
4. The salicylate effect on immune precipitation is reversible, and appears to be due to inactivation of antibody.
5. Salicylate was more effective in preventing specific precipitation than other anions of a lyotropic series tested.