Cellobiose, glucose, xylose and arabinose were identified chromatographically among the degradation products of cellulose irradiated by mercury arc. An 18 in. square ofscoured cotton duck was hung vertically between two Hanovia high Alpine sun lamps emitting powerful spectra from 2,200 to 20, 000 Ã…. After 4, 8, 16, 24 and 48 hr., unpurified degradation products amounted to 0 128, 0. 143, 0. 223, 0.257 and 0.422 gm., respectively. Chromatography showed 5 distinct spots, four having the same coloration and Rf values as D-arabinose, D-xylose, Dglucose and cellobiose. The fifth, lying between cellobiose and glucose, was not identified; it may be a glucopentose or a dipentose. Formation of cellobiose and D-glucose is attributed to hydrolytic cleavage of cellulose; of D-arabinose and D-xylose, to oxidation of glucose followed by decar boxylation of the two resulting carboxylic acids. -- AATA