THE REACTIVITY OF CELLULOSE: II.WATER SORPTION, HEATS OF WETTING, AND THE REACTIONS WITH THALLOUS ETHYLATE IN ETHER, NITRATION MIXTURES, AND HEAVY WATER OF COTTON LINTERS ALTERNATELY WETTED WITH WATER AND DRIED

Cotton linters dewaxed with benzene and alcohol possess a slightly expanded structure attributed to the swelling effect of the alcohol. Storage causes a partial collapse of the linters especially so when moisture is present. Wetting with water followed by rigorous drying produces a marked reduction in accessibility, but with each additional wetting–drying cycle accessibility of the dried linters increases slightly as measured by reaction with thallous ethylate in ether, a nitration mixture, and in hydrogen–deuterium exchange. Differences in nitration found for limited reaction times are obliterated when these reaction times are extended. Increasing accessibility due to repeated wetting and drying is accompanied by lower water sorption and smaller heats of wetting. This anomaly is due to the fact that cellulose samples obtained by alternately wetting and drying dewaxed linters, when stored with a desiccant, compete for the limited amount of water present and adsorb moisture in proportion to their accessibility. Upon further exposure to water the sample of least accessibility, having adsorbed less water, can now adsorb to a greater extent than do the linters of somewhat greater accessibility.The evidence indicates that the difference in accessibility occasioned by repeated wetting and drying is of a physical rather than chemical nature.