Because Kodak stopped manufacturing cellulose nitrate in 1951, the old movie film you have may not be cellulose nitrate-based. The large majority of older consumer motion picture films such as KODAK 8, KODAK Super 8, and KODAK 16 mm film are safety films, and, therefore, not cellulose nitrate film. You may need to use an analytical laboratory to analyze the film base according to procedures shown in ISO 16082.
Learn more about nitrate films.