Some Studies of the Fading of Simple Monoazo Dye

The fastness, on exposure to the light from a carbon arc, of a series of simple morroazo dyes in cellulose acetate film has been measured. A relationship is proposed between the chemical constitution and the order of light fastness of these dyes. The light fastness of each dye has been characterised by a destruction efficiency constant. In defining this quantity, account has been taken of the specific absorbing powers of the dyes for the heterochromatic light used to fade them. Special precautions have been taken to standardise exposures by means of a light flux–time integrator.