Abstract Cellulose was conveniently oxidized by concentrated phosphoric acid added with sodium nitrite ; that is, the cellulose was not apt to be hydrolyzed heavily and the oxidation proceeded smoothly. It was found that carboxyl groups of the oxidized cellulose were largely of the glucuronic type. The oxidized cellulose, whose carboxyl content was more than 8%, was almost soluble in dilute caustic soda solution ; and the mean degree of polymerisation of such oxidized cellulose was nearly two-thirds of that of the untreated cellulose. Some properties of the alkaline solution of the oxidized cellulose were investigated.