The amount of combined sulfur has been determined at all stages in the manufacture of cellulose acetate, including pretreatment, acetylation, and hydrolysis. Little combined sulfur was found during the pretreatment, but after the addition of acetic anhydride, the sulfuric acid combined quantitatively with the cellulose in the intermediate stages of acetylation. At the point where substantially all the hydroxyl groups had been esterified, the combined sulfur content began to drop gradually, and as the reaction time was extended beyond the point where it is normally interrupted to initiate the hydrolysis stage, it continued to drop and was replaced by acetyl. The combined sulfur dropped rapidly during the addition of water for hydrolysis. The lowering of the sulfur content was INDUSTRIAL AND ENGINEERING CHEMISTRY
Several samples of hydrolyzed cellulose acetate, 3040% acetyl, were reacetylated under a variety of reaction conditions.Most of the reactions were carried out without any catalyst, using acetic anhydride as the acetylating agent. Variations were made in the temperature and in the amount of anhydride. Catalysts were also investigated, including sulfuric acid, perchloric acid, zinc chloride and pyridine. Finally, acetylations were made with acetyl chloride and pyridine. The relative reactivities of the primary and secondary hydroxyls were calculated from the total amounts of hydroxyl and the amounts of primary hydroxyl in the products taken during the course of these acetylations. The primary hydroxyls were always more reactive than the secondary. In general, factors which accelerated the reaction diminished the difference in reactivity between primary and secondary hydroxyls. Thus in the uncatalyzed reaction with acetic anhydride at room temperature the primary hydroxyls reacted ten times as fast as the secondary, whereas, in the reaction catalyzed with sulfuric acid they reacted only two and one-half times as fast. Optical rotations throughout these acetylations correlated with the amounts of primary hydroxyl and the acetyl contents.
Because neither 4,7-DMP nor Zn(4.7-DMP)3+2 • -2C104~absorbs above 360 µ, the appearance of an absorption band maximum at 400 µ was attributed to the effect of the 4,7-DMP ligand on the electron density in the coordinated 8-quinolinol ligand. The observed bathochromic shift of 20-30 µ from the maximum for the simple chelate, ZnOx2, is similar to that observed when other nitrogen adducts are formed (75).Some preliminary work has also been performed on the extraction of zinc with 2,9-dimethyl-l,10-phenanthroline alone. This has been sufficient to show that the behavior of this re-
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