Studies on the Vogel's reaction are reviewed. The authors propose a modified Vogel's test method for photographic gelatines in which Vogel's reagent is used in one fiftieth volume of 2% gelatine solution, while in the conventional method the reagent and gelatine solution are used in equal volume. Turbidities are measured at 5 minutes after addition of the reagent into gelatine solution at 30° and after 3 hours ripening at 60°, followed by an addition of 0.3 cc concentrated ammonia and again turbidity is measured each time. By this method, among precipitates of of Vogel's reaction soluble and insoluble components to ammonia can be discriminated. Sixteen gelatines are tested by the method and results are discussed.