Cellulose nitrate sulfate groups

The nitric acid concentration in the nitration acid mixture is usually 20-25%. The degree of nitration can be regulated by changes in the water content. Examples of the solubility and use of cellulose nitrates are given in Table 9-3. As a by-product in the nitration process some cellulose sulfate is also formed (see below). Because this results in instability of the cellulose nitrate, the sulfate groups must be removed by various treatments and the sulfuric acid formed removed by washing. 

Cellulose sulfate has significantly fewer applications than the nitrate. The pyrolysis of cellulose treated with sulfuric acid and containing residual sulfate groups was previously discussed (see Section 7.2). The pyrolysate of this material has a chemical composition similar to that of cellulose pyrolysate. However, the existence of residual sulfate groups favors the reaction ... 

Nitrated cellulose acetate has been prepared, and nucleophilic replacement of nitrate groups of cellulose nitrate with halides has been performed. Oxidative decomposition of cellulose nitrate into a water-soluble material may be brought about by aqueous digestion at high temperature and high pressures, and this finds particular application in the determination of small proportions of the sulfate in cellulose nitrate. A route for the replacement of nitric ester groups in cellulose nitrate by sulfuric ester groups has been reported. ... 

Clark et al [23] at the University of Durham, U.K. have applied XPS to the study of cellulose nitrate and the step by step nitration of cellulose. They have shown which hydroxyl group is most easily accessible for nitration. They have observed sulfate ester from the nitration process at the surface of the nitro cellulose, this is suspected as an initiator of the degradation of N.C. 

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