1045that is, by plotting the oscillation frequencies of the limits of the absorption bands against the logarithms of the relative thicknesses of the solutions (10). Discussion of ResultsAs anticipated, the diketostearic acid is yellow, while the ketohydroxystearic acid is colorless. The position and the persistence of the absorption bands are clearly shown by the curves.The diketostearic acid has a well-defined absorption band in the blue end of the visible spectrum and shows the same light absorption characteristics as the diacetyl and the thymoquinone whose absorption curves are reproduced from Smiles (11) for comparison.The ketohydroxystearic acid shows a less pronounced selective absorption which, however, is entirely located in the ultra-violet region and, therefore, cannot produce visible color. Even the addition of an excess of alkali does not