Diluted emulsion was highly centrif uged to give a clean supernatant gelatin solution free from silver halide grains. The gelatin solution separated from emulsions was compared with a control gelatin solution in the ultraviolet absorption spectra. Thus the adsorption behavior of nucleic acid in gelatin against silver halide grains was investigated on acid, neutral and ammoniacal emulsions. Nucleic acid was, best, in an acid emulsion and slightly in an ammoniacal emulsion, adsorpted by silver halide grains, while in a neutral emulsion it was adsorpted little. The dependence of the nucleic acid adsorption to silver halide grains upon emulsion type was explained principally owing to pH dependence.