Cotton duck samples were treated with derivatives of salicylaldehyde or with copper complexes of these derivatives, and were exposed in a carbon-arc Weather-Ometer. The effectiveness of the treatments in reducing the rate of photo-induced depolymeriza tion of cotton cellulose has been related to (a) the volatility of the treating compounds and complexes, (b) the ability of the compounds to form intramolecular, six-member chelate rings; and (c) the absorption of the treating materials in the spectral region of most intense emmission from the carbon-arc light source. Comparison with oxine and copper oxinate has been made.