Acetate of cellulose is made by a process patented by Cross & Bevan and described in patent No. 9676, 1891. The method is as follows. Dehydrated cellulose is mixed with a concentrated solution of zinc acetate in equal proportions; the mixture is then dried at 110" C, and finely powdered. The powder is mixed in small quantities at a time with acetyl chloride, the proportion being 2 parts of acetyl chloride for each part of zinc acetate used at the first. The mixture is well stirred and cooled, so that the temperature never rises above 30J C. When the reaction is completed the mass is washed with water to remove the zinc salts and dried. To free it from unaltered cellulose, the product is treated with chloroform, which dissolves the cellulose acetate, and, after filtering, the solution is heated; the chloroform then distils over and is collected, and the cellulose acetate is left as a transparent film or sheet.