No abstract

The combination of sulfuric acid with cellulose during cellulose acetate manufacture has long been known but has now been found to be quantitative during the intermediate stages of acetylation. Toward the completion of acetylation and with extended time of reaction, the combined sulfur is gradually replaced by acetyl.2. The loss in sulfur content during isolation of samples from acetylation dopes is avoided by maintaining anhydrous conditions during the dilution prior to precipitation. ; 3. Sulfuric acid combines with cellulose during acetylation to form a cellulose acetate acid sulfate. This acid sulfate is remarkably resistant toward hydrolysis with 14% ammonium hydroxide.4. Samples high in combined sulfur can be reprecipitated without intermittent drying with only slight loss of sulfur.5. Extreme variations in combined sulfur content may be found during the early stages of hydrolysis. Rapid addition of water and low temperature favor the retention of combined sulfur.6. During hydrolysis the combined sulfur drops rapidly to a minimum and then increases slightly on prolonged hydrolysis. The same level of sulfur content was introduced into a sulfur-free cellulose acetate when hydrolyzed with acetic acid, water, and sulfuric acid in amounts equal to those resulting from a cellulose acetylation with sulfuric acid catalyst.7. The amount of combined sulfur at the completion of acetylation and during hydrolysis is roughly proportional over a wide range to the amount of sulfuric acid catalyst used. In the event of partial neutralization of catalyst at the start of hydrolysis, the amount of combined sulfur in the product is determined by the amount of soluble sulfate present during hydrolysis. 8. The conversion of sulfuric to sulfoacetic acid during these cellulose acetylations was negligible. Sulfoacetic acid is a very weak acetylation catalyst which does not combine appreciably with cellulose during acetylation.