A rapid method which compares favorably in accuracy with that of slower methods for measuring the density of cellulosic materials with a gradient column is described. Densities of several cottons before and after chemical modification by partial acetylation, carboxymethylation, aminization, and mercerization are given. Per cent acetyl can be expressed as a function of density in a linear empirical equation over a range of 13 to 42% acetyl with a precision of ± 2%. Density measurements of decrystallized, ball-mill ground, and acid hydrolyzed cottons were in agreement with the generally accepted con cept of the crystalline-amorphous cellulose phase composition in these materials. Cotton from which water was removed by solvent exchange was found to have a high density before, and a low density after, air drying.

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Fluorine and iodine compounds, both organic and inorganic, were tested as flame retardants for cotton. Comparison with bromine and chlorine compounds showed that the effectiveness of the halogens, on an equal weight basis, increases in the order. fluorine, chlorine, bromine, iodine, with the last two about equally effective.

Wrinkle resistance can be imparted to cotton fabrics with a diepoxide when certain coreactant curing agents are used. Such materials coreact to become a part of the finished product and introduce linkages and chemical groups which differ from those obtained when a true catalyst is used. Several coreactants including, for example. phthalic anhydride, citric acid, 1-aminoethyl-2-methyl-imidazoline, triethanolamine, and potassium thiocyanate, were used with 1,3-diglycidylglycerol as the diepoxide. In some cases mere deposition seemed to occur while in other cases cross-linkage was accomplished. Some indications of the types of reaction were obtained from infrared data and from the responses of the treated fabrics to various classes of dyes. In some cases coreaction between the diepoxide and the curing agent appeared to take place at relatively low temperatures, producing improved wrinkle resistance. Phthalic anhydride was used to investigate this aspect in more detail.For comparison with the coreactant materials, several acid salts were used as catalysts, and the results are reported. Among the more suitable acid catalysts are magnesium perchlorate, aluminum sulfate, and zinc fluoborate.The inorganic acid catalysts produced fabrics with excellent durability and wrinkle resistance. Tearing strength losses, however, were greater with epoxide-treated cotton than those observed, at equivalent crease recovery angle, when a typical methylolamide finishing agent with catalyst was used. The durability to alkaline solutions of some of the epoxide finishes applied with coreactant curing agents was not as good as that of fabrics prepared with the inorganic acid catalysts. Tearing strength and wrinkle resistance of epoxide-treated cotton can be improved by inclusion of additives such as polvethylene, acrylic polymer, or silicone, in the finishing bath.